Update CHANGELOG.md

Author: MKodde

CHANGELOG.md

@@ -5,8 +5,11 @@ We will continue to post relevant release notes on the GitHub release page. More
 
 More information about our release strategy can be found in the [Development Guidelines](https://github.com/OpenConext/OpenConext-engineblock/wiki/Development-Guidelines#release-notes) on the EngineBlock wiki.
 
-## 6.3.4
+## 6.3.5
+**Bugfix**
+ - Clean up unused usage of AuthnRequest destination #898
 
+## 6.3.4
 **Bugfix**
  - Whether MFA AuthnContext must be added should be based on original SP #893 #894