More use of url_launcher plugin in Flutter Gallery (#9836)

examples/flutter_gallery/lib/gallery/updates.dart

@@ -6,7 +6,8 @@ import 'dart:async';
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter/services.dart';
+
+import 'package:url_launcher/url_launcher.dart';
 
 typedef Future<String> UpdateUrlFetcher();
 
@@ -42,7 +43,7 @@ class UpdaterState extends State<Updater> {
     if (updateUrl != null) {
       final bool wantsUpdate = await showDialog(context: context, child: _buildDialog());
       if (wantsUpdate != null && wantsUpdate)
-        UrlLauncher.launch(updateUrl);
+        launch(updateUrl);
     }
   }