Fix link to sonic.com

Author: oalders

root/about/sponsors.tx

@@ -432,7 +432,7 @@ money...
       </tr>
       <tr>
         <td>
-          <a target="_blank" rel="noopener nofollow" href="https://www.fastmail.com/">
+          <a target="_blank" rel="noopener nofollow" href="https://www.sonic.com/">
             <img src="/static/images/sponsors/sonic.png" width="170">
           </a>
         </td>