YARN-4341 addendum. Moved the changelog entry from 2.8.0 to 2.9.0.

hadoop-yarn-project/CHANGES.txt

@@ -67,6 +67,9 @@ Release 2.9.0 - UNRELEASED
     ResourceManager to support JvmPauseMonitor as a service.
     (Sunil G via Stevel)
 
+    YARN-4341. add doc about timeline performance tool usage (Chang Li via
+    sjlee)
+
   OPTIMIZATIONS
 
   BUG FIXES
@@ -607,9 +610,6 @@ Release 2.8.0 - UNRELEASED
 
     YARN-4248. REST API for submit/update/delete Reservations. (curino)
 
-    YARN-4341. add doc about timeline performance tool usage (Chang Li via
-    sjlee)
-
   OPTIMIZATIONS
 
     YARN-3339. TestDockerContainerExecutor should pull a single image and not