Debian releases

Re: To PostgreSQL WWW
> Hi,
> 
> could someone please make the list of supported dists on the Ubuntu
> page the following?
> 
> https://www.postgresql.org/download/linux/ubuntu/

Oh, and on https://www.postgresql.org/download/linux/debian/
stretch needs to be removed, which means the "Buster and newer"
comment on arm64 can be removed.

We could also already add bookworm:

* bookworm (12.x)
* bullseye (11.x)
* buster (10.x)
* sid (unstable)

on the following architectures:

* amd64
* arm64
* i386 (buster and older)
* ppc64el

(I'd lowercase all the names to remove some source of confusion.)

Thanks,
Christoph