use pep639

use pep639

The pyproject.toml configuration has been amended to use the updated
:pep:`639` configuration for license, which eliminates loud deprecation
warnings when building the package.   Note this necessarily bumps
setuptools build requirement to 77.0.3.

Also bump black, flake8, see what's coming.

this change is modeled after the same change made in dogpile.cache
which has since been released.

Fixes: #1637
Change-Id: I9a9e22ebaebe0d257f003f5ff5b81088df3c8901