[test] Remove use of unwrapType() from test

This happened to work in both type systems because the property of the
same name exists in both, but technically `unwrapType()` is part of
the old type system and will be deleted soon.

Change-Id: I5620c5f409f0c6fe486b9a4c7a6872ee8deabc09
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/348800
Reviewed-by: Mark Zhou <[email protected]>
Commit-Queue: Nicholas Shahan <[email protected]>

Author: nshahan

tests/dartdevc/const_test.dart

@@ -3,14 +3,14 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import "package:expect/expect.dart";
-import 'dart:_foreign_helper' show JS;
+import 'dart:_foreign_helper' show JS, TYPE_REF;
 import 'dart:_runtime' as dart;
 
 void main() {
   dynamic data = JS('', '[1, 2, 3, 4]');
   Expect.isFalse(data is List<int>);
 
-  var list = dart.constList(data, dart.unwrapType(int));
+  var list = dart.constList(data, TYPE_REF<int>());
   Expect.isTrue(list is List<int>);
   Expect.throws(() {
     list[0] = 0;