Fix potential deadlock during gameplay tests

osu.Game/Screens/Play/GameplayClockContainer.cs

@@ -123,6 +123,10 @@ namespace osu.Game.Screens.Play
 
         public void Restart()
         {
+            // The Reset() call below causes speed adjustments to be reset in an async context, leading to deadlocks.
+            // The deadlock can be prevented by resetting the track synchronously before entering the async context.
+            track.ResetSpeedAdjustments();
+
             Task.Run(() =>
             {
                 track.Reset();