Update docs

[AstraLuma]

Overview

Update the docs for some of the changes:

• Not sure when COUCHDB_CREATE_DATABASE disappeared, but I can't find anything using it
• Pretty sure ERL_COOKIE is a clouseau thing
• COUCHDB_USER/COUCHDB_PASSWORD have been required since the ~cops~good sense broke up the admin party

Testing recommendations

Run the YAML

Checklist

• [x] Documentation reflects the changes;