PostgreSQL driver has been removed from DevStack

Just a heads up that the PostgreSQL DB driver has been removed from DevStack as of today [1]. This was deprecated in Pike due to lack of maintenance and has been on the chopping block since then. If you have jobs that relied on this, it would be advisable to drop these jobs now. I don't think the DevStack team have the resources to maintain this so if someone *really* needed to keep it around, they should probably put together a plugin and consume it that way. Stephen [1] https://review.opendev.org/#/c/678496/