Removes an admin submenu.

Example usage:

– `remove_submenu_page( ‘themes.php’, ‘nav-menus.php’ )`
– `remove_submenu_page( ‘tools.php’, ‘plugin_submenu_slug’ )`
– `remove_submenu_page( ‘plugin_menu_slug’, ‘plugin_submenu_slug’ )`

function remove_submenu_page( $menu_slug, $submenu_slug ) {
	global $submenu;

	if ( ! isset( $submenu[ $menu_slug ] ) ) {
		return false;
	}

	foreach ( $submenu[ $menu_slug ] as $i => $item ) {
		if ( $submenu_slug === $item[2] ) {
			unset( $submenu[ $menu_slug ][ $i ] );
			return $item;
		}
	}

	return false;
}