Remove Expect from core library.

tests/language/licm_test.dart

 // Copyright (c) 2012, 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";
+
 var sum = 0;
 var foo = 0;
 var bar = 1;
 
 test() {
   while (true) {
     if (0 === foo) {
       sum += 2;
       if (1 === bar) {
         sum += 3;
         break;
       }
       break;
     }
   }
 }
 
 main() {
   test();
   Expect.equals(5, sum);
 }