13.2 relnotes: additions/changes suggested by emaste

Wording changes and additions. Deprecations were found in git log;
https://wiki.FreeBSD.org/DeprecationPlan seems to be rather out of
date.

Approved by: delphij
Reviewed by: pauamma, bcr, delphij, jhb, emaste
Differential Revision: https://reviews.freebsd.org/D39016