Update CHANGES.txt for HDFS-8238.

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

@@ -644,6 +644,9 @@ Release 2.8.0 - UNRELEASED
     of Block in UnderReplicatedBlocks and PendingReplicationBlocks).
     (Zhe Zhang via wang)
 
+    HDFS-8238. Move ClientProtocol to the hdfs-client.
+    (Takanobu Asanuma via wheat9)
+
   OPTIMIZATIONS
 
     HDFS-8026. Trace FSOutputSummer#writeChecksumChunks rather than