[css-text-3] Fix markup error

Author: fantasai

css-text-3/Overview.bs

@@ -1314,6 +1314,7 @@ Text Processing</h3>
         white-space-processing-013.xht
         white-space-processing-052.xht
       </wpt>
+    </ul>
 
     <p>Then, the entire block is rendered. Inlines are laid out, taking bidi
       reordering into account, and <a>wrapping</a> as specified by the