ssh: Update to OpenSSH 9.6p1
From the release notes,
This release contains a number of security fixes, some small features
and bugfixes.
The most significant change in 9.6p1 is a set of fixes for a newly-
discovered weakness in the SSH transport protocol. The fix was already
merged into FreeBSD and released as FreeBSD-SA-23:19.openssh.
Full release notes at https://www.openssh.com/txt/release-9.6
Relnotes: Yes
Sponsored by: The FreeBSD Foundation
(cherry picked from commit 069ac18495ad8fde2748bc94b0f80a50250bb01d)
(cherry picked from commit a25789646d7130f5be166cac63d5c8b2b07c4706)