Update CHANGES.txt to move MAPREDUCE-6436 from YARN to MAPREDUCE

(cherry picked from commit 7092d47fc0b3b792dd31f967c01d460dc089f60b)

hadoop-mapreduce-project/CHANGES.txt

@@ -680,6 +680,8 @@ Release 2.6.4 - UNRELEASED
 
   IMPROVEMENTS
 
+  MAPREDUCE-6436. JobHistory cache issue. (Kai Sasaki via zxu)
+
   OPTIMIZATIONS
 
   BUG FIXES

hadoop-yarn-project/CHANGES.txt

@@ -1984,8 +1984,6 @@ Release 2.6.4 - UNRELEASED
 
   IMPROVEMENTS
 
-  MAPREDUCE-6436. JobHistory cache issue. (Kai Sasaki via zxu)
-
   OPTIMIZATIONS
 
   BUG FIXES