The version of pyflakes that is listed in python/tests/minreqs.txt
breaks on Python 3.8 with the following message:

  AttributeError: 'FlakesChecker' object has no attribute 'CONSTANT'

Now that we do not support EOL'd Python versions anymore, we can
update to newer, fixed versions.  It is a good time to do so, before
Python packages start dropping support for Python 3.7 as well!

The new mypy is also a bit smarter about which packages are actually
being used, so remove the now-unnecessary sections from setup.cfg.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20230511035435.734312-27-jsnow@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>