How to Hide the "Dynamic User Directory" Admin Menu

function plt_hide_dynamic_user_directory_menus() {
	//Hide the "Settings → Dynamic User Directory" menu.
	remove_submenu_page('options-general.php', 'user_directory');
}

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

Where do I put this code?