This is issue is to track future support for postgresql 12, due out later this year.
There is a false-positive warning in Jira 8.13.12 for Postgresql 12: "PostgreSQL 12 is not supported. You should migrate to a supported database version.". Necessary corresponding changes need to be done in ATST plugin, the problem is tracked here JRASERVER-72919.
You can safely ignore the warning for Jira 8.13.12+ versions.