Remove Expect from core library.

tests/language/named_argument_test.dart

Index: tests/language/named_argument_test.dart
diff --git a/tests/language/named_argument_test.dart b/tests/language/named_argument_test.dart
index a6a2d39de3328268e125fbc96270076de310993a..0514c2d62e4de129a4437c9cf05250592ad5ff3f 100644
--- a/tests/language/named_argument_test.dart
+++ b/tests/language/named_argument_test.dart
@@ -2,6 +2,8 @@
 // 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";
+
 main() {
   var c1 = ({b, a}) => 'a: $a b: $b';
   var c2 = ({a, b}) => 'a: $a b: $b';