pgsql: Last-minute updates for release notes.

Last-minute updates for release notes.

Security: CVE-2025-8713, CVE-2025-8714, CVE-2025-8715

Branch
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REL_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/18d01671ef2576f7f950c2797a467370bc1a654d

Modified Files
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doc/src/sgml/release-16.sgml | 128 ++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 127 insertions(+), 1 deletion(-)