Updated changelog and package version for Netcode in anticipation of v2.8.1 release

Author: svc-netcode-sdk

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -6,30 +6,12 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 Additional documentation and release notes are available at [Multiplayer Documentation](https://docs-multiplayer.unity3d.com).
 
-## [Unreleased]
+## [2.8.1] - 2026-01-05
 
 ### Added
 
 - test addition
 
-### Changed
-
-
-### Deprecated
-
-
-### Removed
-
-
-### Fixed
-
-
-### Security
-
-
-### Obsolete
-
-
 ## [2.8.0] - 2025-12-15
 
 ### Added