pgsql: Last-minute updates for release notes.

Last-minute updates for release notes.

Security: CVE-2021-23214, CVE-2021-23222

Branch
------
REL_14_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/ddc6917c314ddcf16f56dd2cfd52fbc721760b07

Modified Files
--------------
doc/src/sgml/release-14.sgml | 86 +++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 85 insertions(+), 1 deletion(-)