Remove unused imports in pub.

sdk/lib/_internal/pub/test/descriptor.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.
 
 /// Pub-specific scheduled_test descriptors.
 library descriptor;
 
 import 'package:oauth2/oauth2.dart' as oauth2;
 import 'package:scheduled_test/scheduled_server.dart';
-import 'package:scheduled_test/scheduled_test.dart';
 import 'package:scheduled_test/descriptor.dart';
 
 import '../lib/src/utils.dart';
 import 'descriptor/git.dart';
 import 'descriptor/tar.dart';
 import 'test_pub.dart';
 
 export 'package:scheduled_test/descriptor.dart';
 export 'descriptor/git.dart';
 export 'descriptor/tar.dart';
@@ skipping 141 matching lines @@
           ['https://www.googleapis.com/auth/userinfo.email'],
           expiration).toJson())
     ]);
   }));
 }
 
 /// Describes the application directory, containing only a pubspec specifying
 /// the given [dependencies].
 DirectoryDescriptor appDir([Map dependencies]) =>
   dir(appPath, [appPubspec(dependencies)]);