How to Hide the "IPGP IP Lookup" Admin Menu

function plt_hide_ipgp_ip_address_lookup_widget_menus() {
	//Hide the "Settings → IPGP IP Lookup" menu.
	remove_submenu_page('options-general.php', 'ipgp.php');
}

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

Where do I put this code?