Apply preview setting to ruff formatter

[DimitriPapadopoulos]

It is currently required by the following setting:

quote-style = "preserve"

From https://docs.astral.sh/ruff/settings/#format-quote-style:

• preserve (preview only): Keeps the existing quote character. We don't recommend using this option except for projects that already use a mixture of single and double quotes and can't migrate to using double or single quotes.

Fixes #99 (comment).

[jaraco]

I found the same issue. I was noticing that since we hadn't (yet) enabled formatting in the test suite, it was not breaking not to have this setting. I was hand-adding ruff format --preview when running locally and hoping the preview flag would be unnecessary before I had to add it, but I was recently employing it in an editor and had the same issue, so I made the same change in 29e5d34.