Fix potential test failure in TestSceneMultiplayerReadyButton
Couldn't exactly reproduce https://github.com/ppy/osu/runs/4294316800,
but I found a similar issue via:
```diff
diff --git a/osu.Game.Tests/Visual/Multiplayer/TestSceneMultiplayerReadyButton.cs b/osu.Game.Tests/Visual/Multiplayer/TestSceneMultiplayerReadyButton.cs
index 84b63a5733..29cac9b061 100644
--- a/osu.Game.Tests/Visual/Multiplayer/TestSceneMultiplayerReadyButton.cs
+++ b/osu.Game.Tests/Visual/Multiplayer/TestSceneMultiplayerReadyButton.cs
@@ -3,6 +3,7 @@
using System;
using System.Linq;
+using System.Threading;
using System.Threading.Tasks;
using NUnit.Framework;
using osu.Framework.Allocation;
@@ -81,6 +82,8 @@ private void load(GameHost host, AudioManager audio)
await Client.ToggleReady();
+ Thread.Sleep(1000);
+
readyClickOperation.Dispose();
});
}
```