[FIXED JENKINS-21750] Update changelog

changelog.html

@@ -89,6 +89,9 @@ Upcoming changes</a>
   <li class=rfe>
     Show job name in <em>Schedule Build</em> column tool tip.
     (<a href="https://issues.jenkins-ci.org/browse/JENKINS-25234">issue 25234</a>)
+  <li class=bug>
+    Allow OldDataMonitor to discard promoted-build-plugin Promotions
+    (<a href="https://issues.jenkins-ci.org/browse/JENKINS-26718">issue 26718</a>)
 </ul>
 </div><!--=END=-->
 <h3><a name=v1.598>What's new in 1.598</a> (2015/01/25)</h3>