pgsql: doc: clarify the behavior of unopenable listen_addresses

doc:  clarify the behavior of unopenable listen_addresses

Reported-by: Gurjeet Singh

Discussion: https://postgr.es/m/CABwTF4WYPD9ov-kcSq1+J+ZJ5wYDQLXquY6Lu2cvb-Y7pTpSGA@mail.gmail.com

Backpatch-through: 11

Branch
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REL_11_STABLE

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

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