pgsql: Doc: fix missing comma at the end of a line.

Doc: fix missing comma at the end of a line.

Backpatch to 17, where the line was added.

Reported by Noboru Saito while he was working on translating the file
into Japanese.

Discussion: https://postgr.es/m/20250417.203047.1321297410457834775.ishii%40postgresql.org
Reported-by: Noboru Saito <noborusai@gmail.com>
Reviewed-by: Daniel Gustafs <daniel@yesql.se>
Backpatch-through: 17

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/05883bd6e556bb4d86c7ece4c37080d00cdb0d34

Modified Files
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doc/src/sgml/libpq.sgml | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)