Update secrets-in-dev.mdx (#24447)

Clarify that you should put the .env file in the same directory as your Wrangler configuration file. The previous instruction, to add it to your project root, is confusing as there are different ways to interpret this.

Author: petebacondarwin

src/content/partials/workers/secrets-in-dev.mdx

@@ -6,7 +6,7 @@
 Do not use `vars` to store sensitive information in your Worker's Wrangler configuration file. Use secrets instead.
 :::
 
-Put secrets for use in local development in either a `.dev.vars` file or a `.env` file, in the root of your project.
+Put secrets for use in local development in either a `.dev.vars` file or a `.env` file, in the same directory as the Wrangler configuration file.
 
 :::info
 Choose to use either `.dev.vars` or `.env` but not both. If you define a `.dev.vars` file, then values in `.env` files will not be included in the `env` object during local development.