removal proposal: cad/geda

[Greg Troxel <gdt%lexort.com@localhost>]

Upstream is not only not maintaing this, but has said they aren't and
suggests switching to Ringdove.  The distfile is from 2013.  My best
guess is that nobody is using this, as they would have tried to package
Ringdove.

(While I noticed this because it uses guile20, this removal proposal
stands on its own after evaluating upstream/maintenance/likely-use.)

I'll remove on/after October 13 if no one speaks up that they are using
it.