Use the correct type (integer) for the `$menu_id` parameter in the `wp_get_nav_menu_to_edit()` DocBlock.

Also properly mark the parameter as optional and specify the default value.

Props jaimieolmstead for the initial patch.
Fixes #30540.


git-svn-id: https://develop.svn.wordpress.org/trunk@30627 602fd350-edb4-49c9-b593-d223f7449a82