emulators/virtualbox-ose{,-kmod,-additions}: update to 6.1.50

[vvd]

Summary

Tested build in poudriere and on live system 13.2-p9 amd64.
Run fine for 18 hours on 2 servers with total of 17 VMs.
And on 15 VMs (additions).

PR: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=276437
Changelog: https://www.virtualbox.org/wiki/Changelog-6.1#v50