git am was previously modified to provide --continue for consistency
with rebase, merge etc, and the documentation changed to showing
--continue as the primary form.

Complete the work by replacing remaining uses of --resolved by
--continue, most notably in suggested command reminders.
Signed-off-by: NKevin Bracey <kevin@bracey.fi>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>