Remove unused _save_cjpeg

[radarhere]

Pillow/src/PIL/JpegImagePlugin.py

Lines 848 to 855 in d74fdc4

	def _save_cjpeg(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
	# ALTERNATIVE: handle JPEGs via the IJG command line utilities.
	tempfile = im._dump()
	subprocess.check_call(["cjpeg", "-outfile", filename, tempfile])
	try:
	os.unlink(tempfile)
	except OSError:
	pass

While we test this method, it is never actually called anywhere, so I'm going to suggest removing it.

[hugovk]

Only shows up twice in the history.

Was added but unused in PIL 1.1.1 in 2000: https://github.com/hugovk/PIL/blame/645e19c47556b9086c0d0fdccc1db1b9e6f79f7f/PIL/JpegImagePlugin.py#L473

Part of the fork in 2010: 9a640e3

Tests added in 2014: d283f77