cleanup effectively external AWS regions

[Benjamin Elder]

1. We now have a default fallback for external traffic since #147
2. We're not going to be running in gov cloud regions ourselves.

Attempting to detect and route the based on the AWS region is likely not better than routing them as external traffic. If we even receive an traffic from them, it's probably best mapped by "ok you've reached this cloud run region so here's the default AWS region closest to where the loadbalancer routed you in GCP" instead of "uh hmm I'm going to guess that Gov West is close to oregon or something" and routing in cmd/archeio/app/buckets.go based on IP => AWS region.

ref: https://kubernetes.slack.com/archives/CCK68P2Q2/p1679010160975869?thread_ts=1678915249.434949&cid=CCK68P2Q2

We should wait a bit to make this change. See: #181