Remove @failingTest for the now passing test.

pkg/analysis_server/test/analysis/notification_errors_test.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.
 
 library test.analysis.notification_errors;
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/context_manager.dart';
 import 'package:analysis_server/src/domain_analysis.dart';
@@ skipping 144 matching lines @@
 class NotificationErrorsTest extends AbstractNotificationErrorsTest {}
 
 @reflectiveTest
 class NotificationErrorsTest_Driver extends AbstractNotificationErrorsTest {
   @override
   void setUp() {
     enableNewAnalysisDriver = true;
     generateSummaryFiles = true;
     super.setUp();
   }
-
-  @failingTest
-  @override
-  test_importError() {
-    // The overridden test is failing because we're getting an 'unused import'
-    // hint rather than a URI does not exist error.
-    return super.test_importError();
-  }
 }