Security: end of life dates for FreeBSD stable/12, 12.4, and stable/13

[grahamperrin]

stable/12 and 12.4​

31st December 2023

• <https://lists.freebsd.org/archives/freebsd-announce/2023-December/000113.html>

stable/13​

30th April 2026

• <https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=273795#c4>