Add one more missing FireAndForget call

```csharp
2025-07-17 08:52:06 [error]: An unobserved error has occurred.
2025-07-17 08:52:06 [error]: System.TimeoutException: Server timeout
(30000.00ms) elapsed without receiving a message from the server.
2025-07-17 08:52:06 [error]: at
Microsoft.AspNetCore.SignalR.Client.HubConnection.InvokeCoreAsync(String
methodName, Type returnType, Object[] args, CancellationToken
cancellationToken)
2025-07-17 08:52:06 [error]: at
Microsoft.AspNetCore.SignalR.Client.HubConnection.InvokeCoreAsyncCore(String
methodName, Type returnType, Object[] args, CancellationToken
cancellationToken)
2025-07-17 08:52:06 [error]: at
Microsoft.AspNetCore.SignalR.Client.HubConnection.InvokeCoreAsync(String
methodName, Type returnType, Object[] args, CancellationToken
cancellationToken)
2025-07-17 08:52:06 [error]: at
Microsoft.AspNetCore.SignalR.Client.HubConnectionExtensions.InvokeCoreAsync[TResult](HubConnection
hubConnection, String methodName, Object[] args, CancellationToken
cancellationToken)
2025-07-17 08:52:06 [error]: at
osu.Game.Online.Metadata.OnlineMetadataClient.<isConnectedChanged>b__31_1()
```

Author: peppy

osu.Game/Online/Metadata/OnlineMetadataClient.cs

@@ -12,6 +12,7 @@
 using osu.Game.Configuration;
 using osu.Game.Online.API;
 using osu.Game.Online.API.Requests.Responses;
+using osu.Game.Online.Multiplayer;
 using osu.Game.Users;
 
 namespace osu.Game.Online.Metadata
@@ -116,7 +117,7 @@ private void isConnectedChanged(ValueChangedEvent<bool> connected)
             }
 
             if (IsWatchingUserPresence)
-                BeginWatchingUserPresenceInternal();
+                BeginWatchingUserPresenceInternal().FireAndForget();
 
             if (localUser.Value is not GuestUser)
             {