Remove Unity version support mention from release notes

Author: akiRAM2

docs/releasenote/releasenote-16.5.en.md

@@ -1,4 +1,4 @@
-# Version 16.5.0
+# Version 16.5.0a
 
 ## SDK (Editor Extension Tool for Creating Worlds in Unity)
 
@@ -10,9 +10,6 @@
 - **World Profiler**
     - Added a profiler function to analyze and visualize world performance
 
-- **Unity 6 Support**
-    - Added support for the Unity 6 environment
-
 ### New Features
 
 - **VKC World Setting > Rendering Setting**

docs/releasenote/releasenote-16.5.ja.md

@@ -10,9 +10,6 @@
 - **ワールドプロファイラー**
     - ワールドのパフォーマンスを分析・可視化するプロファイラー機能を追加
 
-- **Unity 6対応**
-    - Unity 6環境での動作をサポート
-
 ### 新機能
 
 - **VKC World Setting > Rendering Setting**