pgsql: Last-minute updates for release notes.

Last-minute updates for release notes.

Security: CVE-2020-25694, CVE-2020-25695, CVE-2020-25696

Branch
------
REL9_6_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/0425151233e018edfc03d2c3fe38f94ef3a67e77

Modified Files
--------------
doc/src/sgml/release-9.6.sgml | 216 ++++++++++++++++++++++++++++--------------
1 file changed, 143 insertions(+), 73 deletions(-)