Update CHANGELOG

Author: EmandM

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -19,7 +19,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 
 ### Changed
 
-- Optimized `NetworkList<T>` indexer setter to skip operations when the new value equals the existing value, improving performance by avoiding unnecessary list events and network synchronization. (#????)
+- Optimized `NetworkList<T>` indexer setter to skip operations when the new value equals the existing value, improving performance by avoiding unnecessary list events and network synchronization. (#3587)
 
 
 ## [2.5.0] - 2025-08-01