Remove unused import

Change-Id: I73796a114cb90d8edc8d47e86a7e7d90ebe33d53
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/112840
Commit-Queue: Paul Berry <paulberry@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Auto-Submit: Paul Berry <paulberry@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

Author: stereotype441

pkg/analyzer/test/src/dart/resolution/enum_test.dart

@@ -2,7 +2,6 @@
 // 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:analyzer/src/error/codes.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';