Update documentation, error messages, etc. to reflect dropping Python 3.8 runtime support

[jtmedley]

The latest version (24.10.0) drops Python 3.8 runtime support via #4452. Error messages and documentation were not updated outside of the changelog.

This creates significant conflicting information between actual requirements and installation instructions, error messages, etc.

Here are a few places (not an exhaustive list) that need updating:

README.md

black/README.md

Lines 39 to 42 in 1b2427a

	### Installation
	_Black_ can be installed by running `pip install black`. It requires Python 3.8+ to run.
	If you want to format Jupyter Notebooks, install with `pip install "black[jupyter]"`.

getting_started.md

black/docs/getting_started.md

Lines 17 to 20 in 1b2427a

	## Installation
	_Black_ can be installed by running `pip install black`. It requires Python 3.8+ to run.
	If you want to format Jupyter Notebooks, install with `pip install "black[jupyter]"`.

docs/faq.md

black/docs/faq.md

Lines 85 to 96 in 1b2427a

	## Which Python versions does Black support?
	Currently the runtime requires Python 3.8-3.11. Formatting is supported for files
	containing syntax from Python 3.3 to 3.11. We promise to support at least all Python
	versions that have not reached their end of life. This is the case for both running
	_Black_ and formatting code.
	Support for formatting Python 2 code was removed in version 22.0. While we've made no
	plans to stop supporting older Python 3 minor versions immediately, their support might
	also be removed some time in the future without a deprecation period.
	Runtime support for 3.7 was removed in version 23.7.0.

docs/integrations/editors.md

black/docs/integrations/editors.md

Lines 237 to 241 in 1b2427a

	#### Installation
	This plugin **requires Vim 7.0+ built with Python 3.8+ support**. It needs Python 3.8 to
	be able to run _Black_ inside the Vim process which is much faster than calling an
	external command.

autoload/black.vim

black/autoload/black.vim

Lines 77 to 80 in 1b2427a

	pyver = sys.version_info[:3]
	if pyver < (3, 8):
	print("Sorry, Black requires Python 3.8+ to run.")
	return False

plugin/black.vim

black/plugin/black.vim

Lines 22 to 30 in 1b2427a

	if v:version < 700 || !has('python3')
	func! __BLACK_MISSING()
	echo "The black.vim plugin requires vim7.0+ with Python 3.6 support."
	endfunc
	command! Black :call __BLACK_MISSING()
	command! BlackUpgrade :call __BLACK_MISSING()
	command! BlackVersion :call __BLACK_MISSING()
	finish
	endif

tox.ini might need updating but I'm not certain:

black/tox.ini

Line 3 in 3dcacdd

envlist = {,ci-}py{37,38,39,310,311,py3},fuzz,run_self

I was halfway through writing this when I saw that #3896 did a very similar thing after 3.7 support was dropped in #3765.

It is not a coincidence that every file changed in that PR also needs changing again for dropping 3.8 support, along with at least a couple others. It would be pretty cool if updates to documentation, error messages, etc. could be more of a standard part of changes like this in the future. Tests also may need updating. Thanks!

[hauntsaninja]

PR welcome!

[JelleZijlstra]

Working on it

[jtmedley]

Good lord that was fast. Thanks!!