fix: Remove cleaning custom spawn/destroy handlers (#326)

No reason to cleaning these handlers. Now implementing own pooling system is harder because initialization must be done after ServerStart()/ClientStart()/HostStart().

Author: rivFox

MLAPI/Core/NetworkingManager.cs

@@ -347,8 +347,6 @@ private void Init(bool server)
             SpawnManager.SpawnedObjectsList.Clear();
             SpawnManager.releasedNetworkObjectIds.Clear();
             SpawnManager.pendingSoftSyncObjects.Clear();
-            SpawnManager.customSpawnHandlers.Clear();
-            SpawnManager.customDestroyHandlers.Clear();
             NetworkSceneManager.registeredSceneNames.Clear();
             NetworkSceneManager.sceneIndexToString.Clear();
             NetworkSceneManager.sceneNameToIndex.Clear();