pkg/scheduled_test: fix analyzer hints

test/scheduled_test/current_schedule_current_task_test.dart

 // Copyright (c) 2013, 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:scheduled_test/scheduled_test.dart';
 
-import 'package:metatest/metatest.dart';
 import '../utils.dart';
 
 void main() {
   expectTestPasses('currentSchedule.currentTask returns the current task while '
       'executing a task', () {
     schedule(() => expect('foo', equals('foo')), 'task 1');
 
     schedule(() {
       expect(currentSchedule.currentTask.description, equals('task 2'));
     }, 'task 2');
@@ skipping 26 matching lines @@
     });
   });
 
   expectTestPasses('currentSchedule.currentQueue is tasks before the schedule '
       'has started', () {
     schedule(() => expect('foo', equals('foo')));
 
     expect(currentSchedule.currentQueue.name, equals('tasks'));
   });
 }