[chore] Remove black and ruff from test-requirements

[sterliakov]

#15210 standardized lint hooks invocations with pre-commit, but did not remove test requirements that became unneeded. Grepping for ruff and black revealed that they are never used directly any longer except for one outdated README notice.

Remove direct dependency on black and ruff, retaining them only in pre-commit configuration. pre-commit does not use local package installations and manages all virtual environments internally.

[brianschubert]

It reads a bit odd when this command uses runtests.py, and the very next line says "You can also run all of the above tests using runtests.py". It may be good to mention the underlying lint command here. FWIW, I always run pre-commit directly, and only just learned that the runtests.py invocation exists.

Suggested change

	python3 runtests.py lint
	pre-commit run -a

[JukkaL]

I prefer to run lint using runtests.py, since it lets me perform several tasks via a single command, such as python3 runtests.py lint self pytest-fast. If we will remove black and ruff from test requirements, we should probably change runtests.py lint to run pre-commit run -a in order to avoid breaking existing workflows.

[brianschubert]

we should probably change runtests.py lint to run pre-commit run -a in order to avoid breaking existing workflows.

It looks like that's already the case :-)

mypy/runtests.py

Lines 68 to 69 in 54a2c6d

	# Lint
	"lint": ["pre-commit", "run", "--all-files"],

[JukkaL]

Nice, forgot about it!

[sterliakov]

I think it's better to still mention python runtests.py lint here since it's difficult to discover by other means. I expanded the preceding paragraph and added pre-commit install mention - does this look better now?

(I also use pre-commit pretty much everywhere so prefer to invoke it directly)

[github-actions]

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

[JukkaL]

Thanks, looks good!