Remove obsolete "interop.js" from browser test scripts.

tools/testing/dart/browser_test.dart

 // Copyright (c) 2011, 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.
 
 part of test_suite;
 
 String getHtmlContents(String title,
                        String scriptType,
                        Path sourceScript) {
   return """
@@ skipping 14 matching lines @@
   <h1> Running $title </h1>
   <script type="text/javascript"
           src="/root_dart/tools/testing/dart/test_controller.js">
   </script>
   <script type="$scriptType" src="$sourceScript"
           onerror="scriptTagOnErrorCallback(null)"
           defer>
   </script>
   <script type="text/javascript"
           src="/root_dart/pkg/browser/lib/dart.js"></script>
-  <script type="text/javascript"
-          src="/root_dart/pkg/browser/lib/interop.js"></script>
 </body>
 </html>""";
 }
 
 String dartTestWrapper(String libraryPathComponent) {
   return """
 import '$libraryPathComponent' as test;
 
 main() {
   print("dart-calling-main");
   test.main();
   print("dart-main-done");
 }
 """;
 }