ingest: Remove reverse column from metadata

Previously this was filled in with empty strings by the custom
`ndjson-to-tsv-and-fasta` script. We've replaced vendored scripts
with `augur curate` commands, so we no longer need this script, but now
the workflow errors on this unexpected column.

As discussed in #209, this
column is not used anyways so just remove it.

ingest/defaults/config.yaml

@@ -72,7 +72,6 @@ curate:
     'date_submitted',
     'sra_accession',
     'abbr_authors',
-    'reverse',
     'authors',
     'institution'
   ]