[WIP] Remove ruff ignore E501

[rwgk]

Description

With PR #4912 we removed black:

-# Black, the code formatter, natively supports pre-commit
-- repo: https://github.com/psf/black-pre-commit-mirror
-  rev: "23.10.1" # Keep in sync with blacken-docs
-  hooks:
-  - id: black

So this isn't true anymore:

pybind11/pyproject.toml

Line 72 in d8565ac

"E501", # Line too long (Black is enough)

I tried to remove that line, but it doesn't make a difference, ruff doesn't produce the E501 error. See dummy test case, which doesn't trigger any ruff errors.

It would be nice to see that error, even if we need to fix manually.

@henryiii: Do you happen to know what suppresses the E501?

Suggested changelog entry:

[timohl]

As far as I can see, Ruff does not include E501 by default, so it has to be added to extend-select.
See docs.astral.sh/ruff/configuration for the default settings:
Only "E4", "E7", "E9" are in select but not E5.