pgsql: docs: Link to the correct protocol version inspection function

docs: Link to the correct protocol version inspection function

The docs for max_protocol_version suggested PQprotocolVersion()
instead of PQfullProtocolVersion() to find out the exact protocol
version. Since PQprotocolVersion() only returns the major protocol
version, that is bad advice.

Author: Jelte Fennema-Nio <postgres@jeltef.nl>
Reviewed-by: Shinya Kato <shinya11.kato@gmail.com>
Discussion: /messages/by-id/CAGECzQSKFxQsYAgr11PhdOr-RtPZEdAXZnHx6U3avLuk3xQaTQ@mail.gmail.com

Branch
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REL_18_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/fa78e5bea53a3096d1df7d1b2d7cbd58d15a9b7a

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