Fixing CHANGES.txt, YARN-138 was missed.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1392341 13f79535-47bb-0310-9956-ffa450edef68

hadoop-yarn-project/CHANGES.txt

@@ -8,6 +8,9 @@ Release 0.23.5 - UNRELEASED
 
   IMPROVEMENTS
 
+    YARN-138. Ensure default values for minimum/maximum container sizes is 
+    sane. (harsh & sseth via acmurthy)
+
     YARN-137. Change the default YARN scheduler to be the CapacityScheduler. 
     (sseth via acmurthy)