suzerain: stale versioning due to typo

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@43663 0bd85f0b-c151-43b9-a1e9-27231104551f
suerain: #2736 remove perfect_mean

It is replaced by perfect_summary, and the lingering postprocessing
should all be done in python-land per #2736 and #2599

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@43664 0bd85f0b-c151-43b9-a1e9-27231104551f