Remove the non-driver versions of several tests

pkg/analysis_server/test/services/completion/dart/label_contributor_test.dart

 // Copyright (c) 2015, 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.
 
 import 'package:analysis_server/protocol/protocol_generated.dart';
 import 'package:analysis_server/src/protocol_server.dart';
 import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
 import 'package:analysis_server/src/services/completion/dart/label_contributor.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import 'completion_contributor_util.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(LabelContributorTest);
-    defineReflectiveTests(LabelContributorTest_Driver);
   });
 }
 
 @reflectiveTest
 class LabelContributorTest extends DartCompletionContributorTest {
+  @override
+  bool get enableNewAnalysisDriver => true;
+
   CompletionSuggestion assertSuggestLabel(String name,
       {int relevance: DART_RELEVANCE_DEFAULT,
       CompletionSuggestionKind kind: CompletionSuggestionKind.IDENTIFIER}) {
     CompletionSuggestion cs =
         assertSuggest(name, csKind: kind, relevance: relevance);
     expect(cs.returnType, isNull);
     Element element = cs.element;
     expect(element, isNotNull);
     expect(element.flags, 0);
     expect(element.kind, equals(ElementKind.LABEL));
@@ skipping 280 matching lines @@
       break;
     foo: case 2:
       continue ^;
     case 3:
       break;
 ''');
     await computeSuggestions();
     assertSuggestLabel('foo');
   }
 }
-
-@reflectiveTest
-class LabelContributorTest_Driver extends LabelContributorTest {
-  @override
-  bool get enableNewAnalysisDriver => true;
-}