pgsql: doc PG 18 relnotes: mv. hash joins and GROUP BY item to General

doc PG 18 relnotes: mv. hash joins and GROUP BY item to General

Reported-by: David Rowley

Discussion: /messages/by-id/CAApHDvqJz+Zf7a6abisqoTGottDSRD+YPx=aQSgCsCKD476vGA@mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/99ddf8615c215bb81655574b9a9f7e8ebb2cb89e

Modified Files
--------------
doc/src/sgml/release-18.sgml | 56 ++++++++++++++++++++++----------------------
1 file changed, 28 insertions(+), 28 deletions(-)