Remove legacy incertae sedis

[vangberg]

Draft – #332 needs to be merged first.

We still have the legacy Name#incertae_sedis field in the database. In preparation for #173 I would like to remove it to reduce the number of edge cases we need to handle.

I have investigated the current state of Name#incertae_sedis in the production database:

There are 16 names with legacy incertae_sedis set:

irb(main):083> nx = Name.where.not(incertae_sedis: [nil, ""])
irb(main):084> nx.size
=> 16

All 16 records have a placement with either a parent or incertae_sedis, which can be verified by running the following:

Name.where.not(incertae_sedis: [nil, ""]).map {|n| [n[:incertae_sedis], n.placement.try(:parent).try(:name), n.placement.try(:incertae_sedis)]}

I interpret that as it being safe to drop this column from the database.