component/slapos: remove cliff version pin

We need the newest version anyway and it does not trigger a problem in OBS

component/slapos/obs.cfg

@@ -183,7 +183,3 @@ configure-command =
     -Dusethreads
 environment +=
   DESTDIR=${buildout:destdir}
-
-[versions]
-# More recently version of cliff uses pbr which will break package build on OBS.
-cliff = 1.4.5