Revert SKBitmap.Encode with SKPngEncoderOptions to previous behavior (2.88.8) (#3014)

* Revert SKBitmap.Encode with SKPngEncoderOptions to previous behavior

* Update SKPixmap.cs

---------

Co-authored-by: Matthew Leibowitz <mattleibow@live.com>

Author: sungaila

binding/SkiaSharp/SKPixmap.cs

@@ -237,7 +237,7 @@ public bool Encode (SKWStream dst, SKEncodedImageFormat encoder, int quality) =>
 				SKEncodedImageFormat.Jpeg =>
 					Encode (dst, new SKJpegEncoderOptions (quality)),
 				SKEncodedImageFormat.Png =>
-					Encode (dst, new SKPngEncoderOptions ()),
+					Encode (dst, SKPngEncoderOptions.Default),
 				SKEncodedImageFormat.Webp when quality == 100 =>
 					Encode (dst, new SKWebpEncoderOptions (SKWebpEncoderCompression.Lossless, 75)),
 				SKEncodedImageFormat.Webp =>