Drop support for older Barback versions.

test/transformer/runs_a_transformer_group_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 '../serve/utils.dart';
 
 const GROUP = """
 import 'package:barback/barback.dart';
 
 import 'transformer.dart';
 
 class RewriteGroup implements TransformerGroup {
   RewriteGroup.asPlugin();
 
   Iterable<Iterable> get phases => [[new RewriteTransformer.asPlugin()]];
 }
 """;
 
 main() {
-  withBarbackVersions("any", () {
-    integration("runs a transformer group", () {
-      d.dir(appPath, [
-        d.pubspec({
-          "name": "myapp",
-          "transformers": ["myapp/src/group"]
-        }),
-        d.dir("lib", [d.dir("src", [
-          d.file("transformer.dart", REWRITE_TRANSFORMER),
-          d.file("group.dart", GROUP)
-        ])]),
-        d.dir("web", [
-          d.file("foo.txt", "foo")
-        ])
-      ]).create();
+  integration("runs a transformer group", () {
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "transformers": ["myapp/src/group"]
+      }),
+      d.dir("lib", [d.dir("src", [
+        d.file("transformer.dart", REWRITE_TRANSFORMER),
+        d.file("group.dart", GROUP)
+      ])]),
+      d.dir("web", [
+        d.file("foo.txt", "foo")
+      ])
+    ]).create();
 
-      createLockFile('myapp', pkg: ['barback']);
+    createLockFile('myapp', pkg: ['barback']);
 
-      pubServe();
-      requestShouldSucceed("foo.out", "foo.out");
-      endPubServe();
-    });
+    pubServe();
+    requestShouldSucceed("foo.out", "foo.out");
+    endPubServe();
   });
 }