remove bdist_wheel universal if py3-only

[thatch]

The snippet I have in skel for setup.cfg includes the following:

[bdist_wheel]
universal = true

When a project has requires_python that only makes it work on py3, this is a little silly to make a py2.py3 wheel that only works on 3. That config value should be removed if requires_python does not allow py2.

from packaging.specifiers import SpecifierSet

spec = SpecifierSet(requires_python)
if not "2.8" in spec:
  # then remove 

Then add something in opine/suggestions that checks for it in setup.cfg, and runs after UseDeclarativeConfig.