Changed link to Ukrainian version in index.html

Author: shorodilov

index.html

@@ -20,7 +20,7 @@ <h2>Course Materials</h2>
       <a href="_build/html/en/index.html">English version</a></li>
     <li>
       <!--suppress HtmlUnknownTarget -->
-      <a href="_build/html/ua/index.html">Ukrainian version</a>
+      <a href="_build/html/uk/index.html">Ukrainian version</a>
     </li>
   </ul>
 </div>