STYLE upgrade flake8 to version 4+

[MarcoGorelli]

flake8 isn't getting updated by the auto-update job because the url

pandas/.pre-commit-config.yaml

Lines 38 to 39 in 7131268

	- repo: https://gitlab.com/pycqa/flake8
	rev: 3.9.2

has changed. flake8 is now hosted at https://github.com/PyCQA/flake8 .

Task here is to change the repo url, set the latest flake8 version, and fixup any errors which result from

pre-commit run flake8 --all-files

[pranay101]

I would like to work on this.

[MarcoGorelli]

there's already #45053