Docs: Add a comment about the $title global usage in various admin files.

This should make it clear that the variable is used as part of the HTML `<title>` tag on admin screens.

Props ravipatel, hellofromTonya, sabernhardt, audrasjb, SergeyBiryukov.
Fixes #53729.

git-svn-id: https://develop.svn.wordpress.org/trunk@51475 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/authorize-application.php

@@ -62,6 +62,7 @@ if ( isset( $_POST['action'] ) && 'authorize_application_password' === $_POST['a
 	}
 }
 
+// Used in the HTML title tag.
 $title = __( 'Authorize Application' );
 
 $app_name    = ! empty( $_REQUEST['app_name'] ) ? $_REQUEST['app_name'] : '';