Remove obsolete plugin_test_win (#86826)

dev/devicelab/bin/tasks/plugin_test_win.dart

-// Copyright 2014 The Flutter Authors. 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:flutter_devicelab/framework/framework.dart';
-import 'package:flutter_devicelab/tasks/plugin_tests.dart';
-
-Future<void> main() async {
-  await task(combine(<TaskFunction>[
-    PluginTest('apk', <String>['-a', 'java', '--platforms=android']),
-    PluginTest('apk', <String>['-a', 'kotlin', '--platforms=android']),
-  ]));
-}