pgsql: doc: clarify the effect of concurrent work_mem allocations

doc: clarify the effect of concurrent work_mem allocations

Reported-by: Sami Imseih

Discussion: /messages/by-id/66590882-F48C-4A25-83E3-73792CF8C51F@amazon.com

Backpatch-through: 11

Branch
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REL_13_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/c8afad9e634979ed0ba411cd38d659de8593ae18

Modified Files
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doc/src/sgml/config.sgml | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)