'pg_global' cannot be used as default_tablespace.

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/13/bug-reporting.html
Description:

Tablespace 'pg_global' is one of the two auto-generated tablespace by
initdb, and 'pg_global' should not be used as the default_tablespace, since
it is used for shared system catalogs. However, none of these information is
recorded in the doc
https://www.postgresql.org/docs/11/runtime-config-client.html and
https://www.postgresql.org/docs/11/manage-ag-tablespaces.html. In case of
some mishandling to use 'pg_global' as a default_tablespace value, it is
better to record it in the doc of
https://www.postgresql.org/docs/11/manage-ag-tablespaces.html.