Fix double dd tag.

Author: gkellogg

index.html

@@ -2993,7 +2993,7 @@ <h3>application/ld+json</h3>
     </dl>
   <dt class="changed">Optional parameters:</dt>
   <dd class="changed">
-    <dd>None</dd>
+    None.
   </dd>
   <dt>Encoding considerations:</dt>
   <dd>See <a data-cite="RFC8259#section-11">RFC&nbsp;8259, section 11</a>.</dd>