Remove explicit dependency on ceph RPM

The libvirt storage driver uses librbd.so for its functionality.
RPM will automatically add a dependency on the library, so there
is no need to have an explicit dependency on the ceph RPM itself.
This allows newer Fedora distros to avoid pulling in the huge
ceph RPM, in favour of just having the libraries installed

libvirt.spec.in

@@ -649,10 +649,6 @@ Requires: device-mapper
 # For multipath support
 Requires: device-mapper
 %endif
-%if %{with_storage_rbd}
-# For RBD support
-Requires: ceph
-%endif
 %if %{with_storage_sheepdog}
 # For Sheepdog support
 Requires: sheepdog