Log Message:
Update a couple of comments that reference Python packages

Those comments were written before converters/unoconv and textproc/
py-Levenshtein were imported. Point to what's in pkgsrc, rather than to
upstream URLs (in the case of py-Levenshtein, an older, unmaintained
version). (I'm not going to change anything to do with Tryton right
now, given the recent related build breakage.)