zuul-worker element: use python3-libselinux for fedora
zuul-worker element: use python3-libselinux for fedora

It seems Fedora 31 has completely remvoed python-libselinux, so this
now causes a build failure.

Change-Id: I563896f1caa1a68781f10b27cd7d9cf2606aaa17

openstack-infra/project-config,openstack-infra/project-config