Update CHANGELOG.md

Author: nixonsam

CHANGELOG.md

@@ -1,7 +1,7 @@
 # Change Log
 
 ## [4.10.0](https://github.com/plivo/plivo-python/tree/v4.10.0) (2020-08-24)
-- Added powerpack for mms.
+- Add Powerpack for MMS.
 
 ## [4.9.0](https://github.com/plivo/plivo-python/tree/v4.8.1) (2020-07-21)
 - Add retries to other regions for voice requests.