pgsql: doc: clarify the behavior of unopenable listen_addresses

doc: clarify the behavior of unopenable listen_addresses

Reported-by: Gurjeet Singh

Discussion: /messages/by-id/CABwTF4WYPD9ov-kcSq1+J+ZJ5wYDQLXquY6Lu2cvb-Y7pTpSGA@mail.gmail.com

Backpatch-through: 11

Branch
------
REL_11_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/14e60252c441d39f244497b60ea60e69d52e39f8

Modified Files
--------------
doc/src/sgml/config.sgml | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)