deprecating Forward-Secure Sealing (FSS) in the journal

[Zbigniew Jędrzejewski-Szmek <zbyszek@xxxxxxxxx>]

Hi,

I'd like to start $subject. First, we'd just add an entry in NEWS
and make the key generation code print a warning, but then in a release
or few remove the code.

See https://github.com/systemd/systemd/pull/28433/commits/1ecd1a994733d.

If you're using FSS, please speak up.

Zbyszek