New postgres image version is available on docker registry with tag 12-debezium - https://hub.docker.com/r/openlmis/postgres/tags
Upgrade instructions for each version can be found on postgres page https://www.postgresql.org/docs/current/upgrading.html
In order to properly upgrade database additional steps might be required, depending on the deployed instance:
It is recommended to make full backup before any upgrade to prevent data loss.
After upgrade in every service, make sure that the demo-data builds successfully with new images (versions of services should be changed in ref-distro). If not, you should also:
Upgrade postgres for demo-data
Upgrade postgres for base service and then change it for every service