cmd/upspin-setupstorage: replace GCP bucket setup with local disk setup
cmd/upspin-setupstorage: replace GCP bucket setup with local disk setup

The Cloud Storage bucket setup has been moved to
gcp.upspin.io/cmd/upspin-setupstorage-gcp.

Change-Id: I8d3e595747cba5c81eb9ed9a334f061ce667e07e
Reviewed-on: https://upspin-review.googlesource.com/9301
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>

upspin/upspin,upspin/upspin