rpm: drop createrepo dependency

createrepo isn't directly used by this package, but by
qubes-core-dom0-linux instead. Lets keep that dependency only there,
especially when it's changed to createrepo_c.

rpm_spec/core-dom0.spec.in

@@ -85,7 +85,6 @@ Requires:       xen-hvm
 Requires:       xen-hvm-stubdom-linux
 Requires:       libvirt-daemon-xen >= 3.3.0-7
 %endif
-Requires:       createrepo
 Requires:       cronie
 Requires:       scrypt
 # for qubes-hcl-report