emulators/virtualbox-ose-*: VirtualBox 7.X: license changed from GNU GPLv2 to GNU GPLv3

PR: 294588
Reported by: ykla <yklaxds@gmail.com>
Approved by: vbox@ (vvd@)
Approved by: db@, yuri@ (Mentors, implicit)
MFH: 2026Q2

(cherry picked from commit cb332df6030b77100b2a380016bc719533fd5ef0)