Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/global/deactivate/removes_precompiled_snapshots_test.dart

-// Copyright (c) 2014, 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 '../../descriptor.dart' as d;
-import '../../test_pub.dart';
-
-main() {
-  initConfig();
-  integration('removes precompiled snapshots', () {
-    servePackages((builder) => builder.serve("foo", "1.0.0"));
-
-    schedulePub(args: ["global", "activate", "foo"]);
-
-    schedulePub(
-        args: ["global", "deactivate", "foo"],
-        output: "Deactivated package foo 1.0.0.");
-
-    d.dir(cachePath, [d.dir('global_packages', [d.nothing('foo')])]).validate();
-  });
-}