noindex old staging docs

[phila82r]

The the old staging environment (https://staging.docs.dfuse.io/) is

1. Being indexed by Google - no staging environment should be indexed by search engines.
2. Online -- it’s not needed anymore and should be taken down.

If, for some reason we still need this staging environment, please add this meta to all pages: <meta name="robots" content="noindex">

This will stop crawlers from indexing the staging environment. If we can shut it down, let’s just take the server down.