How to Hide the "404 Redirect" Admin Menu

function plt_hide_404_simple_redirect_menus() {
	//Hide the "Settings → 404 Redirect" menu.
	remove_submenu_page('options-general.php', 'fourzerofour');
}

add_action('admin_menu', 'plt_hide_404_simple_redirect_menus', 11);

Where do I put this code?