Only run the golden tests on the vm (dart-lang/yaml_edit#9)

pkgs/yaml_edit/test/golden_test.dart

diff --git a/pkgs/yaml_edit/test/golden_test.dart b/pkgs/yaml_edit/test/golden_test.dart
index 687be11..c1f65b8 100644
--- a/pkgs/yaml_edit/test/golden_test.dart
+++ b/pkgs/yaml_edit/test/golden_test.dart
@@ -2,9 +2,12 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+@TestOn('vm')
 import 'dart:io';
 import 'dart:isolate';
 
+import 'package:test/test.dart';
+
 import 'test_case.dart';
 
 /// This script performs snapshot testing of the inputs in the testing directory