Update CHANGELOG.md

Author: oleibman

CHANGELOG.md

@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 
 - Phpstan Version 2. [PR #4384](https://github.com/PHPOffice/PhpSpreadsheet/pull/4384)
 - Start migration to Phpstan level 9. [PR #4396](https://github.com/PHPOffice/PhpSpreadsheet/pull/4396)
+- Calculation locale logic moved to separate class. [PR #4398](https://github.com/PHPOffice/PhpSpreadsheet/pull/4398)
 
 ### Moved