ament_pep257 uses deprecated pydocstyle

[InvincibleRMC]

It currently still works but has been deprecated in favor of ruff. However as of astral-sh/ruff#659 there is not currently a Python api that could be used to replace it. And even if it did work ruff is not available via package managers yet.

Some possible solutions are the following:

1. Add warning into ament_pep257 that it might break in the future
2. Hold out for a ruff api replacement that could be dropped in pydocstyles' place in the future
3. Add a deprecation warning then in some future version deprecate in favor of some future ament_ruff

[mjcarroll]

While ruff is interesting, as you mentioned there isn't a Python API that makes it readily available to be used.

When discussing in the weekly maintenance triage, it was also pointed out that flake8 also likely covers most of what we need from pep257.

In the short term, a pull request adding a deprecation warning for ament_pep257 (option 3) would be acceptable. Thanks for bringing this up.