Remove unintentional dependency on analysis_server

pkg/analyzer_plugin/test/src/utilities/test_all.dart

 // Copyright (c) 2017, 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 'change_builder/test_all.dart' as change_builder;
+import 'string_utilities_test.dart' as string_utilities;
 
 main() {
   defineReflectiveSuite(() {
     change_builder.main();
+    string_utilities.main();
   }, name: 'utilities');
 }