[lint] fix deprecation warning printed to stderr by black

Summary:
This makes the linter fail when running arc lint --everything but for some reason it did not trigger when running arc lint -- somefile.py.
Note that this change in flag adds some extra rules, in addition to string splitting, as described here: https://black.readthedocs.io/en/stable/the_black_code_style/future_style.html#preview-style

These rules are likely to be accepted in the future standard and look like improvements.

Test Plan: arc lint --everything

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D13882