Remove Expect from core library.

tests/corelib/indexed_list_access_test.dart

 // Copyright (c) 2011, 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 "package:expect/expect.dart";
+
 // Check that indexed access to lists throws correct exception if index
 // is not int.
 
 main() {
   checkList(new List.fixedLength(10));
   var growable = new List();
   growable.add(1);
   growable.add(1);
   checkList(growable);
 }
@@ skipping 27 matching lines @@
 
 
 getIt(var a, var i) {
   return a[i];
 }
 
 
 putIt(var a, var i) {
   a[i] = null;
 }