How to Hide the "Excellent transition gallery" Admin Menu

function plt_hide_excellent_transition_gallery_menus() {
	//Hide the "Settings → Excellent transition gallery" menu.
	remove_submenu_page('options-general.php', 'excellent-transition-gallery');
}

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

Where do I put this code?