Bug#1078198: openjdk-23: keep out of testing

[Emilio Pozuelo Monfort]

Package: openjdk-23
Version: 23~34ea-1
Severity: serious

openjdk-23 is a non-LTS release, and we won't ship with it. It can
stay in unstable and may be useful to bootstrap newer OpenJDK releases,
but it shouldn't migrate to testing.

Cheers,
Emilio