dist: rpm: correct systemd post-uninstall scriptlet
dist: rpm: correct systemd post-uninstall scriptlet

The post-uninstall scriptlet requires a parameter, but older versions
of rpm survived without it. Fedora 31's rpm is more strict, so supply
this parameter.

avikivity/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla