run0: drop -a short switch for --area=

run0: drop -a short switch for --area=

Follow-up for f44e7a8c11833563d558c208c76cdcc0df7de022

This breaks the rule stated at the beginning of help_sudo_mode():

> NB: Let's not go overboard with short options: we try to keep a modicum of compatibility with
> sudo's short switches, hence please do not introduce new short switches unless they have a roughly
> equivalent purpose on sudo. Use long options for everything private to run0.