Start state display as hidden

Would otherwise flicker for a few frames when a new user was added to
the list of participants.

osu.Game/Screens/Multi/RealtimeMultiplayer/Participants/StateDisplay.cs

@@ -18,6 +18,7 @@ namespace osu.Game.Screens.Multi.RealtimeMultiplayer.Participants
         public StateDisplay()
         {
             AutoSizeAxes = Axes.Both;
+            Alpha = 0;
         }
 
         private MultiplayerUserState status;