How to Hide the "Enhancements" Admin Menu

function plt_hide_admin_site_enhancements_menus() {
	//Hide the "Tools → Enhancements" menu.
	remove_submenu_page('tools.php', 'admin-site-enhancements');
}

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

Where do I put this code?