Update index.html

Playground/index.html

@@ -425,7 +425,7 @@
                     <a target='_new' href="https://www.netlify.com/">Deployed by Netlify</a>
                 </div>
                 <div class='link'>
-                    <a target='_new' href="http://www.html5gamedevs.com/forum/16-babylonjs/">Forum</a>
+                    <a target='_new' href="https://forum.babylonjs.com/">Forum</a>
                 </div>
                 <div class='link'>
                     <a target='_new' href="https://www.babylonjs.com/sandbox">Sandbox</a>
@@ -487,4 +487,4 @@
         </script>
     </body>
 
-</html>
+</html>