Remove deprecated Expect from the libraries.

tests/language/duplicate_interface_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.
 // Check fail because of cycles in super class relationship.
 
 library duplicateInterfaceTest;
 
+import 'package:expect/expect.dart';
 import "duplicate_interface_lib.dart" as alib;
 
 class InterfB { }
 
 // Ok since InterfB and alib.InterfB are not the same interface
 class Foo implements InterfB , alib.InterfB { }
 
 
 main() {
   Expect.isTrue(new Foo() is InterfB);
   Expect.isTrue(new Foo() is alib.InterfB);
 }