Fix CHANGES.txt for commit r889086: HDFS-813 should be HDFS-824

git-svn-id: https://svn.apache.org/repos/asf/hadoop/hdfs/trunk@889090 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -558,7 +558,7 @@ Release 0.21.0 - Unreleased
 
     HDFS-192. Fix TestBackupNode failures. (shv)
 
-    HDFS-813. Stop lease checker in TestReadWhileWriting.  (szetszwo)
+    HDFS-824. Stop lease checker in TestReadWhileWriting.  (szetszwo)
 
 Release 0.20.2 - Unreleased