How to Hide the "jQuery T(-) Countdown Widget" Admin Menu

function plt_hide_jquery_t_countdown_widget_menus() {
	//Hide the "Settings → jQuery T(-) Countdown Widget" menu.
	remove_submenu_page('options-general.php', 't-countdown');
}

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

Where do I put this code?