[packman] retiring 12.3 in packman

[Olaf Hering]

On Thu, May 21, Stefan Botter wrote:

> We should agree on a deadline for 12.3 - perhaps already end of May -
> and then stop building an publishing packages.

Once PMBS has settled later today I will disable the 12.3 repo.

I assume I could also wipe it right away and the mirrors will still keep
the current state. But I'm not sure about that, so I leave the actual
wiping from the prj conf to you.

Olaf