Remove references to the linter plugin

pkg/analysis_server/test/single_context_manager_test.dart

 // Copyright (c) 2016, 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 test.analysis_server.src.single_context_manager;
 
 import 'dart:core';
 
 import 'package:analysis_server/src/single_context_manager.dart';
 import 'package:analysis_server/src/utilities/null_string_sink.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:analyzer/src/util/glob.dart';
-import 'package:linter/src/plugin/linter_plugin.dart';
 import 'package:path/path.dart' as path;
 import 'package:plugin/manager.dart';
 import 'package:plugin/plugin.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import 'context_manager_test.dart' show TestContextManagerCallbacks;
 import 'mocks.dart';
 
 main() {
@@ skipping 503 matching lines @@
     resourceProvider.modifyFile(file, 'new contents');
     await pumpEventQueue();
     return expect(filePaths[file], equals(callbacks.now));
   }
 
   void _processRequiredPlugins() {
     List<Plugin> plugins = <Plugin>[];
     plugins.addAll(AnalysisEngine.instance.requiredPlugins);
     plugins.add(AnalysisEngine.instance.commandLinePlugin);
     plugins.add(AnalysisEngine.instance.optionsPlugin);
-    plugins.add(linterPlugin);
     ExtensionManager manager = new ExtensionManager();
     manager.processPlugins(plugins);
   }
 }
 
 class TestUriResolver extends UriResolver {
   @override
   Source resolveAbsolute(Uri uri, [Uri actualUri]) {
     return null;
   }
 }