docs: remove references to docs before v10

Author: jennifer-shehane

docs/api/cypress-api/env.mdx

@@ -164,8 +164,6 @@ Cypress.env() // => {foo: 'foo', baz: 'quux', host: 'http://server.dev.local'}
 
 ### From a plugin
 
-<WarningPluginsFile />
-
 Here's an example that uses `Cypress.env` to access an environment variable
 that's been
 [dynamically set in a plugin](/guides/tooling/plugins-guide).

docs/api/plugins/configuration-api.mdx

@@ -83,8 +83,6 @@ for more information on how this works.
 
 ### Switch between multiple configuration files
 
-<WarningPluginsFile />
-
 This means you can do things like store multiple configuration files and switch
 between them like:
 

docs/api/plugins/writing-a-plugin.mdx

@@ -11,8 +11,6 @@ The Plugins API allows you to hook into and extend Cypress behavior.
 
 :::
 
-<WarningPluginsFile />
-
 ## Plugins API
 
 The [`setupNodeEvents`](/guides/references/configuration#setupNodeEvents)
@@ -180,5 +178,3 @@ exported function again.
 This enables you to iterate on plugin code even with Cypress already running.
 
 <!-- map often used refs to deeplinks within page !-->
-
-[legacypluginsfile]: /guides/references/legacy-configuration#Plugins

docs/guides/core-concepts/writing-and-organizing-tests.mdx

@@ -257,8 +257,6 @@ results, and easily shared or browsed through our web interface. To learn more a
 
 ### Plugins file
 
-<WarningPluginsFile />
-
 The plugins file is a special file that executes in Node before the project is
 loaded, before the browser launches, and during your test execution. While the
 Cypress tests execute in the browser, the plugins file runs in the background

docs/guides/references/changelog.mdx

@@ -4871,7 +4871,7 @@ to Cypress 7.0.**
   [#8714](https://github.com/cypress-io/cypress/issues/8714).
 - The bundled Node.js version was upgraded from `12.18.3` to `14.16.0`. This
   could change the behavior of code within the `pluginsFile` when using the
-  [bundled Node.js version](/guides/references/legacy-configuration#Node-version) of
+  bundled Node.js version of
   Cypress. Addressed in
   [#15292](https://github.com/cypress-io/cypress/pull/15292).
 - Installing Cypress on your system now requires Node.js 12+. Addresses
@@ -7956,7 +7956,7 @@ _Released 10/31/2019_
 
 **Features:**
 
-- [testFiles](/guides/references/legacy-configuration#Folders--Files) now also accepts
+- `testFiles` now also accepts
   an Array of glob patterns when specifying what test files to load in
   configuration. Addresses
   [#5401](https://github.com/cypress-io/cypress/issues/5401).
@@ -8043,12 +8043,12 @@ _Released 10/23/2019_
   pass `false` to the `--config-file` to not use any configuration file.
   Addresses [#1369](https://github.com/cypress-io/cypress/issues/1369).
 - You can now use your system's Node version by setting the
-  [nodeVersion](/guides/references/legacy-configuration#Node-version) to `system` in
+  `nodeVersion` to `system` in
   your configuration. This Node version will be used to build files in your
-  [integrationFolder](/guides/references/legacy-configuration#Folders--Files) and
-  [supportFile](/guides/references/legacy-configuration#Folders--Files) and also be used
+  `integrationFolder` and
+  `supportFile` and also be used
   to execute code in your
-  [pluginsFile](/guides/references/legacy-configuration#Folders--Files). If not set,
+  `pluginsFile`. If not set,
   Cypress will continue to use the Node version bundled with Cypress. Addresses
   [#4432](https://github.com/cypress-io/cypress/issues/4432).
 - [.dblclick()](/api/commands/dblclick) now accepts `position`, `x`, and `y`
@@ -9618,8 +9618,8 @@ _Released 11/2/2018_
 - We updated how we handle
   [trashAssetsBeforeRuns](/guides/references/configuration#Screenshots)
   behavior. We now trash the contents of the
-  [screenshotsFolder](/guides/references/legacy-configuration#Folders--Files) and
-  [videosFolder](/guides/references/legacy-configuration#Folders--Files) directories
+  `screenshotsFolder` and
+  `videosFolder` directories
   instead of trashing the directories themselves. This helps maintain any file
   access permissions for the directories. Fixes
   [#1943](https://github.com/cypress-io/cypress/issues/1943) and
@@ -10020,7 +10020,7 @@ _Released 6/28/2018_
   elements with `position: sticky`. Fixes
   [#1475](https://github.com/cypress-io/cypress/issues/1475).
 - Fixed a bug where changing the
-  [integrationFolder](/guides/references/legacy-configuration#Folders--Files) in Windows
+  `integrationFolder` in Windows
   would lead to errors with plugins. Fixes
   [#1704](https://github.com/cypress-io/cypress/issues/1704).
 - Cypress no longer crashes when a 3rd party server sends invalid `gzip`
@@ -12174,7 +12174,7 @@ _Released 11/27/2016_
 **Breaking Changes:**
 
 - Previously, we auto-magically included all files within
-  [`cypress/support`](/guides/references/legacy-configuration#Folders--Files).
+  `cypress/support`.
   This has now [gone away](/guides/references/error-messages#Support-file-missing-or-invalid) and we've
   simplified this to automatically including a single `cypress/support/index.js`
   file. That single file acts as the entry point meaning you should `import` or
@@ -12184,7 +12184,7 @@ _Released 11/27/2016_
   the implementation of it has. We will automatically seed a
   `cypress/support/index.js` file for you (even on existing projects). The file
   location of `cypress/support/index.js` can be changed with the new
-  [`supportFile`](/guides/references/legacy-configuration#Folders--Files)
+  `supportFile`
   option in your `cypress.json`. This feature can also be turned off by
   specifying `supportFile: false`.
 
@@ -13326,12 +13326,12 @@ _Released 03/28/2016_
 - Cypress no longer looks at your `tests` directory for test files. Now, by
   default, it looks in the `cypress/integration` directory.
 - We've removed the configuration option `testFolder` and renamed it to
-  [`integrationFolder`](/guides/references/legacy-configuration#Folders--Files) inside
+  `integrationFolder` inside
   of the `cypress.json`.
 - We've renamed the `cypress` npm package to be `cypress-cli`. You'll see a
   giant deprecation warning until your scripts have been updated to reference
   `cypress-cli`.. You can also uninstall the `cypress` npm package.
-- Added new [`fileServerFolder`](/guides/references/legacy-configuration#Folders--Files)
+- Added new `fileServerFolder`
   configuration option that can mount a directory other than your project root
   when using Cypress as a web server.
 

docs/guides/references/configuration.mdx

@@ -4,10 +4,7 @@ title: Configuration
 
 :::caution
 
-This guide is for Cypress 10+ and the new JavaScript configuration file format.
-
-If you are on an older version of Cypress that uses `cypress.json`, please see
-the [legacy configuration](/guides/references/legacy-configuration) guide.
+This guide is for Cypress 10+.
 
 For more info on upgrading configuration to Cypress 10, see the
 [migration guide](/guides/references/migration-guide#Migrating-to-Cypress-100).
@@ -628,13 +625,6 @@ internal behavior of Cypress using the [`on`](/api/plugins/writing-a-plugin#on)
 and [`config`](/api/plugins/writing-a-plugin#config) arguments, and is valid as
 an [`e2e`](#e2e) or [`component`](#component) testing specific option.
 
-:::info
-
-This function was added in Cypress version `10.0.0` to replace the deprecated
-[plugins file](/guides/references/legacy-configuration#Plugins).
-
-:::
-
 :::cypress-config-example
 
 ```ts