fix(NetworkClient): Remove OnHostClientObjectDestroy (#3964)

NetworkServer::UnSpawnInternal already does everything we need to do, and since the identity is removed from spawned before the ObjectDestroyMessage is sent the lookup never succeeds and the spawned.Remove was already done.
- NetworkServer.Destroy calls UnSpawnInternal which does all the cleanup.

Assets/Mirror/Core/NetworkClient.cs

@@ -495,7 +495,8 @@ internal static void RegisterMessageHandlers(bool hostMode)
             // 'message id not found' errors.
             if (hostMode)
             {
-                RegisterHandler<ObjectDestroyMessage>(OnHostClientObjectDestroy);
+                // host mode doesn't need destroy messages (see NetworkServer::UnSpawnInternal)
+                RegisterHandler<ObjectDestroyMessage>(_ => { });
                 RegisterHandler<ObjectHideMessage>(OnHostClientObjectHide);
                 RegisterHandler<NetworkPongMessage>(_ => { }, false);
                 RegisterHandler<SpawnMessage>(OnHostClientSpawn);
@@ -1320,17 +1321,6 @@ internal static void OnObjectSpawnFinished(ObjectSpawnFinishedMessage _)
         }
 
         // host mode callbacks /////////////////////////////////////////////////
-        static void OnHostClientObjectDestroy(ObjectDestroyMessage message)
-        {
-            //Debug.Log($"NetworkClient.OnLocalObjectObjDestroy netId:{message.netId}");
-
-            // remove from owned (if any)
-            if (spawned.TryGetValue(message.netId, out NetworkIdentity identity))
-                connection.owned.Remove(identity);
-
-            spawned.Remove(message.netId);
-        }
-
         static void OnHostClientObjectHide(ObjectHideMessage message)
         {
             //Debug.Log($"ClientScene::OnLocalObjectObjHide netId:{message.netId}");