Remove Widgets Demo, it's broken and doesn't provide any value over Stocks App

sky/examples/widgets/main.sky

Index: sky/examples/widgets/main.sky
diff --git a/sky/examples/widgets/main.sky b/sky/examples/widgets/main.sky
deleted file mode 100644
index 506b0ff837521d1945a72af0108950f539768c38..0000000000000000000000000000000000000000
--- a/sky/examples/widgets/main.sky
+++ /dev/null
@@ -1,15 +0,0 @@
-#!mojo mojo:sky_viewer
-<!--
-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
--->
-<sky>
-<import src="/sky/framework/debug/shake-to-reload.sky" />
-<script>
-import 'widgets_app.dart';
-void main() {
-  new WidgetsApp();
-}
-</script>
-</sky>