Update SkiaSharp on Android

[TopperDEL]

There is an open issue with SkiaSharp that prevents using the latest version. This issue is to remin me of the fact that at the moment of writing SkiaSharp 2.80.2 is the only working version of SkiaSharp on Android. Using 2.80.3 leads to Streams being empty after coming back from the ThumbnailGenerator in the UnoHelper-library. Once the base-issue is resolved the SkiaSharp-Dependency could be removed from the StorjGalleryUpload-Droid-App. We could then simply use the indirect dependency via UnoHelpers.