trivial: CI: run debian-s390x first
trivial: CI: run debian-s390x first

It finishes the quickest of the builds so it will speed up CI

vathpela/fwupd,superm1/fwupd,vathpela/fwupd,superm1/fwupd,fwupd/fwupd,fwupd/fwupd,hughsie/fwupd,superm1/fwupd,vathpela/fwupd,hughsie/fwupd,fwupd/fwupd,hughsie/fwupd,fwupd/fwupd,vathpela/fwupd,hughsie/fwupd