How to Hide the "Lightbox with PhotoSwipe" Admin Menu

function plt_hide_lightbox_photoswipe_menus() {
	//Hide the "Settings → Lightbox with PhotoSwipe" menu.
	remove_submenu_page('options-general.php', 'lightbox-photoswipe');
}

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

Where do I put this code?