Remove --py2 argument

[cdce8p]

Remove the --py2 argument. It already creates a parser error.

mypy/mypy/main.py

Lines 1267 to 1271 in 7a94183

	if options.python_version < (3,):
	parser.error(
	"Mypy no longer supports checking Python 2 code. "
	"Consider pinning to mypy<0.980 if you need to check Python 2 code."
	)

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[hauntsaninja]

Thanks! It's been long enough since we dropped support that this makes sense