doc: Add PROPERTY GRAPH to the access privilege tables

doc: Add PROPERTY GRAPH to the access privilege tables

The SELECT privilege can be granted on a property graph, and its
privileges can be examined with psql's \dp command, but property
graphs were missing from both summary tables in the "Privileges"
section: the applicable object types for SELECT in the privilege
abbreviations table, and the per-object-type row in the summary of
access privileges table.  Add the missing entries so the tables match
the actual behavior described for the SELECT privilege and in GRANT.

While at it, also add a test for \dp on a property graph.

Author: Shinya Kato <shinya11.kato@gmail.com>
Reviewed-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAOzEurScgwLDXQmNFnDZANGAMMiva9GnLH_kO8qGtGVHUvVk2A%40mail.gmail.com