Adapt to archiso releng now having cloud-init support built in

I'm not familiar with this sub-project, and only just stumbled upon it via archiso#2 (closed) from archiso!125 (closed), but...

... it seems to me that there is a little bit of overlap, and possible simplification possible here now, with the recent introduction of cloud-init support in archiso releng? See archiso#27 (closed), today's commits, and upcoming archiso!117 (closed).