Docs: Improve the docblock of wp_admin_bar_edit_menu().

What age were you when you learned that there's a `$user_id` global, as well as `$user_ID` global? I was today years old.

Props pento, mukesh27.
Fixes #43448.



git-svn-id: https://develop.svn.wordpress.org/trunk@44586 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/admin-bar.php

@@ -677,6 +677,8 @@ function wp_admin_bar_shortlink_menu( $wp_admin_bar ) {
  *
  * @global WP_Term  $tag
  * @global WP_Query $wp_the_query
+ * @global int      $user_id      The ID of the user being edited. Not to be confused with the
+ *                                global $user_ID, which contains the ID of the current user.
  *
  * @param WP_Admin_Bar $wp_admin_bar
  */