Clean up and simplify SeaRISE-Antarctica example.

I've removed the scripts actually used to do the SeaRISE-Antarctica examples
because I don't forsee them getting good maintenance.  They remain in the
stable0.4 and stable0.5 releases.  Specifically, the `experiments.sh` and
post-processing scripts have been removed, but this also allowed the stuff that
generated forcing files to be removed.  There were no other major changes.