fix extra line added to CHANGES.txt in HDFS-6902 cherry-pick

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -301,8 +301,6 @@ Release 2.6.0 - UNRELEASED
 
     HDFS-6892. Add XDR packaging method for each NFS request (brandonli)
 
-    HDFS-6938. Cleanup javac warnings in FSNamesystem (Charles Lamb via wheat9)
-
     HDFS-6902. FileWriter should be closed in finally block in
     BlockReceiver#receiveBlock() (Tsuyoshi OZAWA via Colin Patrick McCabe)