Bug#878852: Remove postgresql-9.6 from testing

[Christoph Berg <christoph.berg@credativ.de>]

Package: postgresql-9.6
Version: 9.6.5-1
Severity: serious

postgresql-9.6 is being replaced by postgresql-10, it can already be
removed from testing.

There's a few dependencies that are updated in unstable, but have not
transitioned yet:
  postgresql-mysql-fdw
  orafce
  postgresql-pllua

Waiting for NEW processing:
  pgextwlist

Fixed in experimental:
  repmgr

Unfixed, but in the works:
  skytools3

Release team:
For the unblocking the python3.6-as-default transition, please
consider removing postgresql-9.6 pgextwlist repmgr skytools3 from
testing, and speeding up the transition of postgresql-mysql-fdw orafce postgresql-pllua

Thanks,
Christoph