package/postgresql: security bump version to 13.4

Release notes:
https://www.postgresql.org/about/news/postgresql-134-128-1113-1018-9623-and-14-beta-3-released-2277/

Fixes CVE-2021-3677:
https://www.postgresql.org/support/security/CVE-2021-3677/



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>