Add changelog item category

Author: jayaddison

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Removed
+
 - Drop support for Python versions prior to 3.6
 
 ## [1.0.2](https://github.com/jeancochrane/pytest-flask-sqlalchemy/releases/tag/v1.0.2) (2019-04-03)