Remove duplicated CHANGELOG.md line

Author: koppor

CHANGELOG.md

@@ -28,7 +28,6 @@ Note that this project **does not** adhere to [Semantic Versioning](http://semve
 - We reintroduced the index column. [#5844](https://github.com/JabRef/jabref/pull/5844)
 - Filenames of external files can no longer contain curly braces. [#5926](https://github.com/JabRef/jabref/pull/5926)
 - We made the filters more easily accessible in the integrity check dialog. [#5955](https://github.com/JabRef/jabref/pull/5955)
-- We reimplemented and improved the dialog "Customize entry types" [#4719](https://github.com/JabRef/jabref/issues/4719)
 - We reimplemented and improved the dialog "Customize entry types". [#4719](https://github.com/JabRef/jabref/issues/4719)
 
 ### Fixed