chore: remove obsolete JReleaser changelog marker

release-please now manages CHANGELOG.md, so the JRELEASER_CHANGELOG_APPEND
comment is no longer needed.

Author: osiegmar

CHANGELOG.md

@@ -5,7 +5,6 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-<!-- JRELEASER_CHANGELOG_APPEND - Do not remove or modify this section -->
 ## [v4.1.0] - 2025-10-09
 
 ## 🚀 Features