setup: avoid setuptools 67 - it can't handle celery's broken pytz dependency

With setuptools 67 or later, launching Kallithea fails as:

$ gearbox serve -c my.ini --reload
15:56:54,111 ERROR [gearbox] Expected closing RIGHT_PARENTHESIS
pytz (>dev)
~^

The `packaging` vendored in setuptools cannot handle the broken syntax
`Requires-Dist: pytz (>dev)` in
venv/lib/python3.11/site-packages/celery-5.0.5.dist-info/METADATA .

The old celery version currently used by Kallithea is wrong, and setuptools has
moved on after a reasonable grace period. We thus have to work around and avoid
latest setuptools.

See https://github.com/pypa/setuptools/issues/3889 .