📅 Fix release date in CHANGELOG.md

- Update release date from 2024-12-20 to 2025-12-20
- Correct date for v4.0.0-rc1 release

Author: puikinsh

CHANGELOG.md

@@ -5,7 +5,7 @@ All notable changes to AdminLTE will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [4.0.0-rc1] - 2024-12-20
+## [4.0.0-rc1] - 2025-12-20
 
 ### 🎉 Major Modernization Release