Remove Expect from core library.

tests/language/named_parameters3_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.
 // Dart test program for testing named parameters.
 // Specifying named argument for not existing named parameter is run time error.
 
+import "package:expect/expect.dart";
+
 int test(int a, [int b]) {
   return a;
 }
 
 main() {
   bool foundError = false;
   try {
     test(10, x:99);  // 1 positional arg, as expected. Param x does not exist.
   } on NoSuchMethodError catch (e) {
     foundError = true;
   }
   Expect.equals(true, foundError);
 }