Add support to use legacy combo fonts for the counter on legacy skins

osu.Game/Skinning/LegacySkinConfiguration.cs

@@ -15,6 +15,8 @@ namespace osu.Game.Skinning
         public enum LegacySetting
         {
             Version,
+            ComboPrefix,
+            ComboOverlap,
             AnimationFramerate,
             LayeredHitSounds,
         }