Use https for wikisuite.org

They don’t have an automated redirection, nor HSTS preload, so it is
better to directly point to the HTTPS version of their website.

Thanks to @linkmauve

index.html

@@ -219,7 +219,7 @@
                         <h2>Converse.js is supported by:</h2>
                         <ul>
                             <li><a href="https://www.keycdn.com/" target="_blank" rel="noopener"><img style="height: 3em" src="/logo/keycdn.svg" alt="KeyCDN"></a></li>
-                            <li><a href="http://wikisuite.org" target="_blank" rel="noopener"><img style="height: 4em" src="/logo/wikisuite-white.png" alt="WikiSuite"></a></li>
+                            <li><a href="https://wikisuite.org" target="_blank" rel="noopener"><img style="height: 4em" src="/logo/wikisuite-white.png" alt="WikiSuite"></a></li>
                         </ul>
                     </div>