added changelog entry

changelog.html

@@ -92,6 +92,9 @@ Upcoming changes</a>
   <li class=rfe>
     Added a mechanism to control the XML parser behaviour
     (<a href="https://github.com/jenkinsci/jenkins/pull/67">pull request #67</a>)
+  <li class=rfe>
+    Minor UI improvements for Jenkins update center.
+    (<a href="http://issues.jenkins-ci.org/browse/JENKINS-9212">issue 9212</a>)
   <li class='major rfe'>
     Added a mechanism to write views in Groovy. The interface isn't committed yet. We are looking for feedback.
 </ul>