Keep the first of duplicate TIFF tags

[radarhere]

Sequel to #10201

Pillow/Tests/test_file_libtiff.py

Lines 1343 to 1345 in bc7e6f5

	# 16x16 strip with duplicated BitsPerSample and PhotometricInterpretation
	# tags. libtiff keeps the first (8-bit YCbCr, read as 4 bytes/pixel RGBA)
	# while Pillow keeps the last (16-bit RGB, rawmode RGB;16N, 6 bytes/pixel).

If libtiff keeps the first of duplicate tags, then let's do the same.

Pillow/Tests/test_file_libtiff.py

Lines 1329 to 1331 in bc7e6f5

	# 16x16 8-bit greyscale tile, with a PhotometricInterpretation tag that
	# has two values. Pillow reads it as YCbCr (rawmode RGBX, 4 bytes/pixel)
	# while libtiff ignores it and decodes 1 byte/pixel.

If libtiff is ignoring a malformed PhotometricInterpretation tag, then let's do the same.

With these changes, the test no longer fails the C checks from the earlier PR.

The C code can be left in as a defensive measure for when Pillow and libtiff disagree, but this PR stops them from disagreeing in the first place.