Mention that it's useful for determining table names for partitioned
tables as well as for those in inheritance hierarchies.

Author: Ian Lawrence Barwick <barwick@gmail.com>
Reviewed-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAB8KJ=gFmBXP=P9htziOj+WM5PDAK4qc7iGQta+8kUh306kQnw@mail.gmail.com