Release 10.4.0

Author: GrahamCampbell

CHANGELOG.md

@@ -5,7 +5,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [10.4.0] - UPCOMING
+## [10.4.0] - 2020-12-22
 
 [10.4.0]: https://github.com/GitLabPHP/Client/compare/10.3.1...10.4.0