Remove custom expect.dart from Kernel tests

tests/kernel/unsorted/field_dispatcher_test.dart

 // Copyright (c) 2016, 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 'expect.dart';
+import 'package:expect/expect.dart';
 
 class A {
   Function fun;
   A(this.fun);
 }
 
 globalFunctionPositional(int a, [int b = 42]) => a + b;
 
 globalFunctionNamed(int a, {int b: 42}) => a + b;
 
@@ skipping 12 matching lines @@
   Expect.isTrue(new A(globalFunctionPositional).fun(1) == 43);
   Expect.isTrue(new A(globalFunctionNamed).fun(1, b: 2) == 3);
   Expect.isTrue(new A(globalFunctionNamed).fun(1) == 43);
 
   var foo = new Foo(100);
   Expect.isTrue(new A(foo.methodFunctionPositional).fun(1, 2) == 103);
   Expect.isTrue(new A(foo.methodFunctionPositional).fun(1) == 143);
   Expect.isTrue(new A(foo.methodFunctionNamed).fun(1, b: 2) == 103);
   Expect.isTrue(new A(foo.methodFunctionNamed).fun(1) == 143);
 }