Update sortable.html

update links to https

Author: markvantilburg

demos/draggable/sortable.html

@@ -38,7 +38,7 @@
 </ul>
 
 <div class="demo-description">
-<p>Draggables are built to interact seamlessly with <a href="http://jqueryui.com/sortable">sortables</a>.</p>
+<p>Draggables are built to interact seamlessly with <a href="https://jqueryui.com/sortable">sortables</a>.</p>
 </div>
 </body>
 </html>