pg_identify_object return missing 'domain' keyword for domain constraints

Hi,

When I call pg_identify_object on a domain constraint, it produces an
invalid identifier because it omits the 'domain' keyword.

For example, when running it against the us_postal_code_check constraint
from the Create Domain documentation (PostgreSQL 8.4.22 Documentation) - I
expect to receive "us_postal_code_check on domain public.us_postal_code",
but I actually receive "us_postal_code_check on public.us_postal_code".

I've attached a script which demonstrates the issue, as tested on the
postgres:latest docker image (Debian 15.1-1.pgdg110+1).

Adam