Remove unused import

Author: szakarias

test/dot_shorthands_test.dart

@@ -1,7 +1,6 @@
 // Copyright (c) 2025, 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:analyzer/dart/ast/ast.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';