Remove the unused class SingleContextManager

pkg/analysis_server/test/test_all.dart

 // Copyright (c) 2014, 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:test_reflective_loader/test_reflective_loader.dart';
 
 import 'analysis/test_all.dart' as analysis_all;
 import 'analysis_server_test.dart' as analysis_server_test;
 import 'channel/test_all.dart' as channel_test;
 import 'completion_test.dart' as completion_test;
 import 'context_manager_test.dart' as context_manager_test;
 import 'domain_analysis_test.dart' as domain_analysis_test;
 import 'domain_completion_test.dart' as domain_completion_test;
 import 'domain_diagnostic_test.dart' as domain_experimental_test;
 import 'domain_execution_test.dart' as domain_execution_test;
 import 'domain_server_test.dart' as domain_server_test;
 import 'edit/test_all.dart' as edit_all;
 import 'operation/test_all.dart' as operation_test_all;
 import 'plugin/test_all.dart' as plugin_all;
 import 'protocol_server_test.dart' as protocol_server_test;
 import 'protocol_test.dart' as protocol_test;
 import 'search/test_all.dart' as search_all;
 import 'services/test_all.dart' as services_all;
-import 'single_context_manager_test.dart' as single_context_manager_test;
 import 'socket_server_test.dart' as socket_server_test;
 import 'source/test_all.dart' as source_all;
 import 'src/test_all.dart' as src_all;
 
 /**
  * Utility for manually running all tests.
  */
 main() {
   defineReflectiveSuite(() {
     analysis_all.main();
     analysis_server_test.main();
     channel_test.main();
     completion_test.main();
     context_manager_test.main();
     domain_analysis_test.main();
     domain_completion_test.main();
     domain_execution_test.main();
     domain_experimental_test.main();
     domain_server_test.main();
     edit_all.main();
     operation_test_all.main();
     plugin_all.main();
     protocol_server_test.main();
     protocol_test.main();
     search_all.main();
     services_all.main();
-    single_context_manager_test.main();
     socket_server_test.main();
     source_all.main();
     src_all.main();
   }, name: 'analysis_server');
 }