unpin setuptools

unpin setuptools

The pin for ``setuptools<69.3`` in ``pyproject.toml`` has been removed.
This pin was to prevent a sudden change to :pep:`625` in setuptools from
taking place which changes the file name of SQLAlchemy's source
distribution on pypi to be an all lower case name, and the change was
extended to all SQLAlchemy projects to prevent any further surprises.
However, the presence of this pin is now holding back environments that
otherwise want to use a newer setuptools, so we've decided to move forward
with this change, with the assumption that build environments will have
largely accommodated the setuptools change by now.

Change-Id: I0cd9ab0512004669a8f0aa0cb7f560d89a2da2bd