Update changelog

Author: aral

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](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [15.4.0] - In progress…
+## [15.4.0] - 2020-11-04
 
 This release implements a lot of small improvements, some of which have been longstanding.