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

Changelog: https://www.virtualbox.org/wiki/Changelog-6.1#v50

PR: 276437
Approved by: arrowd (mentor), olce
Differential Revision: https://reviews.freebsd.org/D43510
MFH: 2024Q1

(cherry picked from commit 9e318d649a9b1eb79f8b7a97b5436974d7e426f9)