Shorten CHANGELOG.md intro text

CHANGELOG.md

@@ -1,13 +1,9 @@
 # Changelog
 
 All notable changes to this project will be documented in this file.
-This project **does not** adhere to [Semantic Versioning](http://semver.org/).
-This file tries to follow the conventions proposed by [keepachangelog.com](http://keepachangelog.com/).
-Here, the categories "Changed" for added and changed functionality,
-"Fixed" for fixed functionality, and
-"Removed" for removed functionality are used.
-
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 We refer to [GitHub issues](https://github.com/JabRef/jabref/issues) by using `#NUM`.
+Note that this project **does not** adhere to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]