Docs: Update comments in `wp_nav_menu()` tests per the documentation standards.

Includes:

- Fixing a few typos.
- Using the correct format for multi-line comments.
- Removing some comments that duplicate the assertion messages without providing any additional context. 

Follow-up to [54478].

Props SergeyBiryukov.
Merges [54741] to the 6.1 branch.
See #56792, #56946.
Built from https://develop.svn.wordpress.org/branches/6.1@54808


git-svn-id: http://core.svn.wordpress.org/branches/6.1@54360 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.1.1-alpha-54807';
+$wp_version = '6.1.1-alpha-54808';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.