Add missing doc blocks to wp-admin/includes/*.

Fix some egregious uses of tabbing.
Some functions can simply return `apply_filters(...)` instead of setting a variable that is immediately returned.

See #32444.


git-svn-id: https://develop.svn.wordpress.org/trunk@32654 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/user-new.php

@@ -17,6 +17,11 @@ if ( is_multisite() ) {
 }
 
 if ( is_multisite() ) {
+	/**
+	 *
+	 * @param string $text
+	 * @return string
+	 */
 	function admin_created_user_email( $text ) {
 		$roles = get_editable_roles();
 		$role = $roles[ $_REQUEST['role'] ];