Change debounce consideration to use dynamic FPS moving average rather than fixed 60 fps

This should better account for scenarios where user FPS is below 60 fps.
Previously the debounce would unexpectedly be longer than usual for low
FPS scenarios.

osu.Game/Screens/SelectV2/SongSelect.cs

@@ -402,7 +402,7 @@ namespace osu.Game.Screens.SelectV2
             if (debounceQueuedSelection == null) return;
 
             // avoid debounce running early if there's a single long frame.
-            debounceElapsedTime += Math.Min(1000 / 60.0, Clock.ElapsedFrameTime);
+            debounceElapsedTime += Math.Min(1000 / Clock.FramesPerSecond, Clock.ElapsedFrameTime);
 
             if (debounceElapsedTime >= SELECTION_DEBOUNCE)
                 performDebounceSelection();