Reinvestigate EOL message
follow up on https://phabricator.kde.org/T9381
appstream does have an OS meta type now and that has an EOL value for releases, talk to discover peeps about adopting that. also see if we can adopt it instead of bespoke the EOL data in https://cgit.kde.org/distro-release-notifier.git/ -- https://releases.neon.kde.org/eol.json