nixos/acme: do not eat Let's Encrypt's request limits if misconfigured on first try (#266155)

      serviceConfig = commonServiceConfig // {

        Group = data.group;

        # Let's Encrypt Failed Validation Limit allows 5 retries per hour, per account, hostname and hour.

        # This avoids eating them all up if something is misconfigured upon the first try.

        RestartSec = 15 * 60;

        # Keep in mind that these directories will be deleted if the user runs

        # systemctl clean --what=state

        # acme/.lego/${cert} is listed for this reason.