pgsql: doc: Remove link to JSON support in the SQL specification

doc: Remove link to JSON support in the SQL specification

The link used in the documentation is dead, and the only options to have
an access to this part of the SQL specification are not free. Like any
other books referred, just remove the link to keep some neutrality but
keep its reference.

Reported-by: Erik Rijkers
Discussion: /messages/by-id/989abd7d-af30-ab52-1201-bf0b4f33b872@xs4all.nl
Backpatch-through: 12

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/ada0e91f9d435b8c1c185107f3ba4e80966b7d82

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