debugdirstate: deprecate --nodates in favor of --no-dates
We have supported 'no-' prefixes for boolean flag for a few years now,
so I was expecting it to be --no-dates.
I noticed that we have --nodates options for a few more commands
(e.g. `hg diff`), but I'll leave that for another day.
Differential Revision: https://phab.mercurial-scm.org/D4693
#require docutils gettext
$ $TESTDIR/check-gendoc el
checking for parse errors