OpenJDK 21 should be kept in testing, and maybe in trixie

[Matthias Klose]

Control: severity -1 important

Adrian, would you mind to stop playing with OpenJDK without discussing 
things first?  Afaics, you are not involved with OpenJDK maintenance, 
nor involved with the Debian Java team.

OpenJDK 25 drops the Hotspot support for armhf and i386, so it makes 
sense to keep the package in testing, and even in the trixie release.