spec: Bump minimum supported Fedora version to 29
spec: Bump minimum supported Fedora version to 29

Signed-off-by: Cole Robinson <7cd45ff6ad1fb7cf556a02797d774247851499f8@redhat.com>
Reviewed-by: Fabiano Fidêncio <2931bae082ef9bc04523ba759c03a4778316d48f@redhat.com>

libvirt/libvirt-python,libvirt/libvirt-python,libvirt/libvirt-python