Fix typos in changelog (#809)

CHANGELOG.md

@@ -8,7 +8,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ## [unreleased]
 ### Added
 
-## Changed
+### Changed
 - PostBigRequest plugin now acts on PRE_EXECUTE_REQUEST event instead of POST_CREATE_REQUEST
 - CustomizeRequest plugin now acts on POST_CREATE_REQUEST event instead of PRE_EXECUTE_REQUEST
 
@@ -23,7 +23,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Set input encoding for select and update queries
 - Create and configure Managed Resources
 
-## Changed
+### Changed
 - More strict types and type hinting
 - `AdapterInterface` does not extend `ConfigurableInterface` anymore
 - `Http` Adapter does not implement `ConfigurableInterface` anymore