Disable masking of Carousel

The default for carousels should be unmasked as their usage generally
sees them overflowing outside their main usage area (see `bleed`
variables).

osu.Game/Graphics/Carousel/Carousel.cs

@@ -228,6 +228,7 @@ namespace osu.Game.Graphics.Carousel
         {
             InternalChild = Scroll = new CarouselScrollContainer
             {
+                Masking = false,
                 RelativeSizeAxes = Axes.Both,
             };