package/postgresql: bump version to 12.1

Release notes of the bugfix release:
https://www.postgresql.org/about/news/1994/
https://www.postgresql.org/docs/current/release-12-1.html



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>