LP#1455606 remove unused self checkout setting

LP#1455606 remove unused self checkout setting

There is an unused (and apparently never used) org unit setting
related to self checkout:

circ.selfcheck.require_patron_password

This commit removes the redundant unused setting, related
permissions, and related strings.

Thanks to Lynn Floyd with the Anderson County Library for pointing
this out.

Signed-off-by: Jeff Godin <jgodin@tadl.org>
Signed-off-by: Chris Sharp <csharp@georgialibraries.org>
Signed-off-by: Ben Shum <ben@evergreener.net>
Conflicts:
	build/i18n/po/db.seed/db.seed.pot

Signed-off-by: Ben Shum <ben@evergreener.net>