Get rid of all the library tags.

test/serve/unknown_dependency_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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 pub_tests;
-
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
 import 'utils.dart';
 
 main() {
   integration("responds with a 404 unknown dependencies", () {
     d.dir(appPath, [
       d.appPubspec()
     ]).create();
 
     pubGet();
     pubServe();
     requestShould404("packages/foo/nope.dart");
     requestShould404("assets/foo/nope.png");
     requestShould404("dir/packages/foo/nope.dart");
     requestShould404("dir/assets/foo/nope.png");
     endPubServe();
   });
 }