Update ChangeLog.md

Remove the new version 1.7.2

Author: msJinLei

src/Resources/Resources/ChangeLog.md

@@ -18,8 +18,6 @@
         - Additional information about change #1
 -->
 ## Upcoming Release
-
-## Version 1.7.2
 - Updated policy cmdlets to use new api version 2019-06-01 that has new EnforcementMode property in policy assignment.
 - Updated create policy definition help example