How to Hide the "WiKi Style TOC" Admin Menu

function plt_hide_wiki_style_table_of_content_menus() {
	//Hide the "Settings → WiKi Style TOC" menu.
	remove_submenu_page('options-general.php', 'toc');
}

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

Where do I put this code?