BUG #17734: Doc bug: "initial database user" used where "bootstrap superuser" is meant

The following bug has been logged on the website:

Bug reference:      17734
Logged by:          Bryn Llewellyn
Email address:      bryn@yugabyte.com
PostgreSQL version: 15.0
Operating system:   macOS Big Sur Version 11.7.
Description:

See «37.1. The Schema»
(https://www.postgresql.org/docs/current/infoschema-schema.html):

«
This schema automatically exists in all databases. The owner of this schema
is the initial database user in the cluster, and that user naturally has all
the privileges on this schema...
»

See this "pgsql-general" thread:
https://www.postgresql.org/message-id/8A2C8B1B-470B-42F9-9694-C1EDDAC06266@yugabyte.com.

It concluded with the decision the the proper term for the role that the
thread discusses is "bootstrap superuser". The proper term should therefore
be used consistently throughout the PG docs.