Prepare 1.4.0 release

CHANGELOG.md

@@ -4,7 +4,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
-## 1.4.0 (TBA)
+## 1.4.0 (2024-03-15)
 * Allow Symfony 7 ([#18](https://github.com/facile-it/mongodb-messenger-transport/issues/18))
 * Require at least `facile-it/mongodb-bundle` 1.6
 * Drop support for PHP 7.3