Update CHANGELOG.md

Update Keep a changelog URL

Author: Mertsch

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 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/),
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project does adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [5.93.0](https://github.com/microsoftgraph/msgraph-sdk-dotnet/compare/5.92.0...5.93.0) (2025-09-16)