update comment about Office UI Fabric (#21)

Author: akrantz

src/taskpane/taskpane.html

@@ -13,7 +13,7 @@
     <!-- Office JavaScript API -->
     <script type="text/javascript" src="https://appsforoffice.microsoft.com/lib/1.1/hosted/office.js"></script>
 
-    <!-- For the Office UI Fabric, go to http://aka.ms/office-ui-fabric to learn more. -->
+    <!-- For more information on Office UI Fabric, visit https://developer.microsoft.com/fabric. -->
     <link rel="stylesheet" href="https://static2.sharepointonline.com/files/fabric/office-ui-fabric-core/9.6.1/css/fabric.min.css"/>
 
     <!-- Template styles -->