How to Hide the "Checkout Fields Setting" Admin Menu

function plt_hide_make_checkout_required_fields_optional_or_optional_fields_required_menus() {
	//Hide the "Checkout Fields Setting" menu.
	remove_menu_page('checkout_fields_setting-rk');
}

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

Where do I put this code?