Don't ratelimit admins

[conorsch]

While debugging the service today, I wanted to request several disbursements, to ensure things were working as I expected. Normally only one disbursement per 24h is allowed, but there's a CLI flag:

    -r, --rate-limit <RATE_LIMIT>
            Per-user rate limit (e.g. "10m" or "1day") [default: 1day]

Restarting the service with e.g. --rate-limit 5m is enough for quick interactive testing, but it'd be nice if galileo were smart enough to recognize Discord admins (typically, but not always, Penumbra Labs staff) and declined to rate limit them.