Drop false claims of support Python 3.8 or 3.9
    
    Recent changes (in particular, use of the new "structural pattern
    matching" syntax, which was introduced in Python 3.10) were already
    incompatible with Python <3.10, but neither the tox settings nor
    the project metadata had been updated to reflect this fact.
    
    Fedora 35, the oldest currently supported branch of Fedora, already
    ships with Python 3.10 by default, so we don't drop support for any
    current Fedora releases.