Update index.html

Update web-animations-js version to include the [fix for TypeErrors when using groups](web-animations/web-animations-next#423).

Author: alancutter

iconpopups/step2/index.html

@@ -5,7 +5,7 @@
   <link href="https://fonts.googleapis.com/css?family=Roboto:300,300italic,400,400italic|Material+Icons" rel="stylesheet" type="text/css" />
   <link href="../shared/codelab.css" rel="stylesheet" type="text/css" />
   <link href="site.css" rel="stylesheet" type="text/css" />
-  <script src="https://cdn.rawgit.com/web-animations/web-animations-js/2.1.2/web-animations-next.min.js"></script>
+  <script src="https://cdn.rawgit.com/web-animations/web-animations-js/2.1.5/web-animations-next.min.js"></script>
   <script src="../shared/codelab.js"></script>
   <script src="site.js"></script>
 </head>
@@ -26,4 +26,4 @@
 </div>
 
 </body>
-</html>
+</html>