Bug 1198452 - Update the "What's Deployed" URL for new revision location

The revision files are now located at:
https://treeherder.allizom.org/revision.txt
https://treeherder.mozilla.org/revision.txt

ui/help.html

@@ -602,7 +602,7 @@
   </div>
   <div class="col-xs-6">
     <a class="midgray pull-right"
-       href="https://whatsdeployed.paas.allizom.org/?owner=mozilla&repo=treeherder&name[]=Stage&url[]=https://treeherder.allizom.org/media/revision&name[]=Prod&url[]=https://treeherder.mozilla.org/media/revision">What's Deployed?</a>
+       href="https://whatsdeployed.paas.allizom.org/?owner=mozilla&repo=treeherder&name[]=Stage&url[]=https://treeherder.allizom.org/revision.txt&name[]=Prod&url[]=https://treeherder.mozilla.org/revision.txt">What's Deployed?</a>
   </div>
 </div>