pkg/scheduled_test: fix analyzer hints

test/descriptor/nothing_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 'dart:io';
 
 import 'package:path/path.dart' as path;
 import 'package:scheduled_test/descriptor.dart' as d;
 import 'package:scheduled_test/scheduled_test.dart';
 
-import 'package:metatest/metatest.dart';
 import 'utils.dart';
 
 void main() {
   expectTestPasses("nothing().create() does nothing", () {
     scheduleSandbox();
 
     d.nothing('foo').create();
 
     schedule(() {
       expect(new File(path.join(sandbox, 'foo')).exists(),
@@ skipping 37 matching lines @@
     schedule(() {
       new Link(path.join(sandbox, 'link')).createSync('nonexistent');
     });
     d.nothing('link').validate();
   }, (error) {
     expect(error.toString(),
         matches(r"^Expected nothing to exist at '[^']+[\\/]link', but found "
             r"a link\.$"));
   });
 }