Update ChangeLog.md

Add missing change log in ChangeLog.md

Author: erich-wang

src/HDInsight/HDInsight/ChangeLog.md

@@ -18,6 +18,7 @@
         - Additional information about change #1
 -->
 ## Upcoming Release
+* Call out breaking changes
 
 ## Version 2.0.1
 * Fixed miscellaneous typos across module