Dont use the default config in ToRgba32

Author: brianpopow

src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs

@@ -343,7 +343,7 @@ private void Write8BitColor<TPixel>(Stream stream, ImageFrame<TPixel> image, Spa
             Span<Rgba32> rgbColors = rgbColorsBuffer.GetSpan();
 
             ReadOnlySpan<TPixel> quantizedColors = quantized.Palette.Span;
-            PixelOperations<TPixel>.Instance.ToRgba32(Configuration.Default, quantizedColors, rgbColors);
+            PixelOperations<TPixel>.Instance.ToRgba32(this.configuration, quantizedColors, rgbColors);
 
             int idx = 0;
             foreach (Rgba32 color in rgbColors)