Tox: use sitepackages
    
    Tox is creating a virtual environment before execution.
    With python 3.12 the virtual env does not include any
    more setuptools, so use setuptools from the globally
    installed packages.
    
    Signed-off-by: Florence Blanc-Renaud <flo@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>