relnotes: Mention sshd restart issue

[emaste]

Summary

After updating it is necessary to reboot (as is the documented process) or at least run service sshd restart.

PR: 263489

[emaste]

website/content/en/releases/13.1R/relnotes.adoc

59

This (specifying a reboot) is definitely true for src upgrades:

make buildworld
make buildkernel KERNCONF=YOUR_KERNEL_HERE
make installkernel KERNCONF=YOUR_KERNEL_HERE
                                                [1]
<reboot in single user>                         [3]
etcupdate -p                                    [5]
make installworld
etcupdate -B                                    [4]
make delete-old                                 [6]
<reboot>

I believe it is also true for freebsd-update, but at least the FreeBSD handbook documentation of freebsd-update appears to be missing a step or two. https://docs.freebsd.org/en/books/handbook/cutting-edge/