PostgreSQL 15 RC2 + GA release dates

Hi,

We are planning a PostgreSQL 15 RC2 release for October 6, 2022. We are 
releasing a second release candidate due to the revert of an 
optimization around the GROUP BY clause.

We are still planning the PostgreSQL 15 GA release for October 13, but 
we may push this to October 20 based on reports from the RCs.

Thanks,

Jonathan