EOL business

[Harald Sitter]

I've drafted up two MRs

lts removal: https://invent.kde.org/sysadmin/bugzilla-bot/-/merge_requests/33

support removal:
https://invent.kde.org/sysadmin/bugzilla-bot/-/merge_requests/34

The latter tries to avoid the word support, being so ambiguous, while
conveying that things just won't get releases anymore.

The basic timeline would then be as suggested:
With the release of 6.4.5 the 6.4 series turns almost_eol and with the
release of 6.4.6 it turns eol.

HS