Remove unused import

Author: ditman

lib/web_ui/test/canvaskit/canvaskit_api_tt_on_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'package:js/js_util.dart' as js_util;
-
 import 'package:test/bootstrap/browser.dart';
 import 'package:test/test.dart';
 import 'package:ui/src/engine.dart';