am: replace uses of --resolved with --continue

am: replace uses of --resolved with --continue

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: Kevin Bracey <redacted>
Signed-off-by: Junio C Hamano <redacted>