Update PEP 708 to clarify a few things
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com> Co-authored-by: C.A.M. Gerlach <CAM.Gerlach@Gerlach.CAM> Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com> Co-authored-by: Stefano Rivera <github@rivera.za.net>