Incorrect and missing docs for range_intersect_agg

range_intersect_agg is documented to return anymultirange (on this page[1]), but it actually returns a range.

In addition, range_intersect_agg also accepts a multirange as its parameter, but that's not documented on the same page. Note that range_agg does *not* accept a multirange (possibly already added for PG15, see this[2]).

Thanks,

Shay

[1] https://www.postgresql.org/docs/current/functions-aggregate.html

[2] https://www.mail-archive.com/pgsql-hackers@lists.postgresql.org/msg105057.html