release version 6.0.9 -- changelog file version update.

Author: tapashmajumder

CHANGELOG.md

@@ -2,7 +2,7 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
-## [6.0.8](https://github.com/Iterable/swift-sdk/releases/tag/6.0.8)
+## [6.0.9](https://github.com/Iterable/swift-sdk/releases/tag/6.0.8)
 #### Fixed
 - set preferUserId to true when using updateUser using userId