Update CHANGELOG.md

Author: Karthikeyan

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 ## [Release 2.6.5](https://github.com/aws/aws-sdk-android/releases/tag/release_v2.6.5)
 
-###Enhancements:
+### Enhancements:
 
 - **Amazon Polly**
   - Added support for new voices - `Matthew` and `Takumi`.