Remove custom expect.dart from Kernel tests

tests/kernel/unsorted/instance_getters_and_setters_test.dart

Index: tests/kernel/unsorted/instance_getters_and_setters_test.dart
diff --git a/tests/kernel/unsorted/instance_getters_and_setters_test.dart b/tests/kernel/unsorted/instance_getters_and_setters_test.dart
index f61ebe53878094f084889c22119a2b028dd97c25..4430a62836822de2fd6f6d2d96bfbf10b5535066 100644
--- a/tests/kernel/unsorted/instance_getters_and_setters_test.dart
+++ b/tests/kernel/unsorted/instance_getters_and_setters_test.dart
@@ -2,7 +2,7 @@
 // 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 {
   var field;