How to Hide the "URL Rotator Manager" Admin Menu

function plt_hide_url_rotator_manager_menus() {
	//Hide the "Tools → URL Rotator Manager" menu.
	remove_submenu_page('tools.php', 'wp_url_rotator_manager');
}

add_action('admin_menu', 'plt_hide_url_rotator_manager_menus', 11);

Where do I put this code?