Small improvements to a couple of pages of the starting guides (#6564)

* Simplify `_build` explanation

Where `mix` comes from is secondary to this bullet point. The important
bit is the `_build` directory.

* Fix small typo

Author: siiky

guides/directory_structure.md

@@ -20,7 +20,7 @@ When we use `mix phx.new` to generate a new Phoenix application, it builds a top
 
 We will go over those directories one by one:
 
-  * `_build` - a directory created by the `mix` command line tool that ships as part of Elixir that holds all compilation artifacts. As we have seen in "[Up and Running](up_and_running.html)", `mix` is the main interface to your application. We use Mix to compile our code, create databases, run our server, and more. This directory must not be checked into version control and it can be removed at any time. Removing it will force Mix to rebuild your application from scratch.
+  * `_build` - a directory that holds all compilation artifacts, created by the `mix` command line tool (shipped as part of Elixir). As we have seen in "[Up and Running](up_and_running.html)", `mix` is the main interface to your application. We use Mix to compile our code, create databases, run our server, and more. This directory must not be checked into version control and it can be removed at any time. Removing it will force Mix to rebuild your application from scratch.
 
   * `assets` - a directory that keeps source code for your front-end assets, typically JavaScript and CSS. These sources are automatically bundled by the `esbuild` tool. Static files like images and fonts go in `priv/static`.
 

guides/request_lifecycle.md

@@ -157,7 +157,7 @@ Next, we need to add files to the `lib/hello_web/controllers/hello_html` directo
 
 Phoenix will see the template file and compile it into an `index(assigns)` function, similar as before. There is no runtime or performance difference between the two styles.
 
-Also note the controller name (`HelloController`) and the view name (`HelloHTML`) and their respective files, `hello_controller.ex` and `hello_html.ex` all follow the same naming convention.  and are named after each other. You could name the directory anything you want, as long as you update the `embed_templates` setting accordingly, but it's best to follow conventions.
+Also note the controller name (`HelloController`) and the view name (`HelloHTML`) and their respective files, `hello_controller.ex` and `hello_html.ex` all follow the same naming convention, and are named after each other. You could name the directory anything you want, as long as you update the `embed_templates` setting accordingly, but it's best to follow conventions.
 
 ```console
 lib/hello_web