[fix] replace polyfill.io with cloudflare equivalent

Author: tnfssc

fixtures/dom/public/renderer.html

@@ -80,7 +80,7 @@
 
     <div id="output"></div>
 
-    <script src="https://cdn.polyfill.io/v2/polyfill.min.js"></script>
+    <script src="https://cdnjs.cloudflare.com/polyfill/v2/polyfill.min.js"></script>
     <script src="renderer.js"></script>
   </body>
 </html>