The note about the future that started with end of life 13.0 seems to be misplaced. It explicitly did not affect the FreeBSD 12.x series of releases.
Comment out the containing section, but not the note.
https://github.com/grahamperrin/freebsd-doc/commit/00b6369bc6ef49de6fe9bbbe4e149f641a9152cc OK'd by @gjb in response to an email from me to (private) lists.
This review first, then I can make some other minor changes/corrections …
The originally approved diff https://reviews.freebsd.org/file/data/d44efk4yvbliysh73l6f/PHID-FILE-gnvy2yjbbphvrre3hwbi/D37369.diff became non-applicable
From today's https://github.com/grahamperrin/freebsd-doc/commit/8c2db4e0e1fa15f332b0247b984972016be71f4f on branch releng/12.4 in my fork, I used GitHub to produce a new diff:
– 51c783aae83fadc8adddbb732f797c14efbbc8f7 committed: