Remove references to the linter plugin

pkg/analysis_server/test/context_manager_test.dart

Index: pkg/analysis_server/test/context_manager_test.dart
diff --git a/pkg/analysis_server/test/context_manager_test.dart b/pkg/analysis_server/test/context_manager_test.dart
index 27c954fee6fd5bed2eb3379d9b6ba343a19bc169..14f458c9b8802e4ceb6d4919e15331d3854c6df7 100644
--- a/pkg/analysis_server/test/context_manager_test.dart
+++ b/pkg/analysis_server/test/context_manager_test.dart
@@ -25,7 +25,6 @@ import 'package:analyzer/src/generated/source_io.dart';
 import 'package:analyzer/src/services/lint.dart';
 import 'package:analyzer/src/summary/summary_file_builder.dart';
 import 'package:analyzer/src/util/glob.dart';
-import 'package:linter/src/plugin/linter_plugin.dart';
 import 'package:linter/src/rules.dart';
 import 'package:linter/src/rules/avoid_as.dart';
 import 'package:path/path.dart' as path;
@@ -1800,7 +1799,6 @@ abstract class ContextManagerTest {
     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);