Revert "Use native async/await support in pub."

sdk/lib/_internal/pub_generated/test/upgrade/report/highlights_overrides_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 library pub_tests;
 
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
 main() {
   initConfig();
   integration("highlights overridden packages", () {
     servePackages((builder) => builder.serve("overridden", "1.0.0"));
 
-    d.dir(appPath, [
-      d.pubspec({
+    d.dir(appPath, [d.pubspec({
         "name": "myapp",
         "dependency_overrides": {
           "overridden": "any"
         }
-      })
-    ]).create();
+      })]).create();
 
     // Upgrade everything.
     pubUpgrade(output: new RegExp(r"""
 Resolving dependencies\.\.\..*
 ! overridden 1\.0\.0 \(overridden\)
 """, multiLine: true));
   });
 }