mages: use the compressed version of the QR code

This helps save some bandwidth and helps with the quicker loading of
the website possibly without losing anything else.

Author: sivaraam

images/commons-app-qr.jpeg

@@ -162,7 +162,7 @@ <h2>Commons Mobile App</h2>
         </div>
 
         <div class="qr-code-div">
-            <img src="images/commons-app-qr.png"/>
+            <img src="images/commons-app-qr.jpeg"/>
         </div>
     </footer>