Move HDFS-8326 out of CHANGES.txt entry for branch-2.7.2.

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

@@ -1831,9 +1831,6 @@ Release 2.7.2 - UNRELEASED
     HDFS-9445. Datanode may deadlock while handling a bad volume.
     (Wlater Su via Kihwal)
 
-    HDFS-8326. Documentation about when checkpoints are run is out of date.
-    (Misty Stanley-Jones via xyao)
-
     HDFS-8767. RawLocalFileSystem.listStatus() returns null for UNIX pipefile.
     (Kanaka Kumar Avvaru via wheat9)