fix: changelog typo

Author: nunomaduro

CHANGELOG.md

@@ -6,7 +6,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 # Release Notes
 
-## [Unreleased](https://github.com/algolia/algoliasearch-client-php/compare/2.2.6...master)
+## [Unreleased](https://github.com/algolia/algoliasearch-client-php/compare/2.3.0...master)
 
 ## [v2.3.0](https://github.com/algolia/algoliasearch-client-php/compare/2.2.6...2.3.0)