Remove invalid Subsampling checks.

[JimBobSquarePants]

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Description

Removed the upper range checks for XY subsampling values in the SOF frame marker.

These must have been left over from before @antonfirsov normalized the upsampling algorithm which seems to work well with everything.

In addition, one of our previously unrecoverable images now no longer crashes and produces (incorrect compared to unfuzzed input, but expected) an output image.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@0c043e1). Click here to learn what that means.
The diff coverage is 87.5%.

@@            Coverage Diff            @@
##             master    #1078   +/-   ##
=========================================
  Coverage          ?   89.83%           
=========================================
  Files             ?     1200           
  Lines             ?    53010           
  Branches          ?     3844           
=========================================
  Hits              ?    47624           
  Misses            ?     4560           
  Partials          ?      826

Impacted Files	Coverage Δ
tests/ImageSharp.Tests/TestImages.cs	100% <ø> (ø)
src/ImageSharp/Formats/Bmp/BmpDecoderCore.cs	94.21% <ø> (ø)
src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs	95.33% <ø> (ø)
src/ImageSharp/Formats/Tga/TgaDecoderCore.cs	88.1% <ø> (ø)
src/ImageSharp/Formats/Gif/LzwDecoder.cs	92.94% <ø> (ø)
src/ImageSharp/Formats/Tga/TgaEncoderCore.cs	98.51% <ø> (ø)
...Sharp.Tests/Formats/Jpg/JpegDecoderTests.Images.cs	100% <100%> (ø)
...c/ImageSharp/Common/Extensions/StreamExtensions.cs	93.33% <75%> (ø)

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