doc/README: Remove mention of freeciv-commits list
Remove mention of freeciv-commits mailing list from doc/README. It's currently not planned to come back as a separate mailing list, and in any case the old list's information isn't correct any more.
Remove mention of freeciv-commits mailing list from doc/README. It's currently not planned to come back as a separate mailing list, and in any case the old list's information isn't correct any more.