relnotes/13.0: note changed AES-NI identification by geli

A user on IRC wondered why his AES-NI-enabled CPU was identified by geli
as "Crypto: accelerated software" on a 13.0-RC, when 12.2 identified it
as "Crypto: hardware".

To help alliviate this confusion, make explicit mention of the change.
While here, also add note to clear up confusion about no functional
change.

Reviewed by: jhb
Differential Revision: https://reviews.freebsd.org/D29281