Fix documentation link.

src/site/resources/documentation.xml

@@ -5,6 +5,5 @@
   <ul>
     <li><a href="documentation/index-m.xhtml">XHTML - one page per section</a></li>
     <li><a href="documentation/index.xhtml">XHTML - single page</a></li>
-    <li><a href="documentation/main.txt">UTF-8 plain text</a></li>
   </ul>
 </div>