x11/budgie-desktop: update to 10.8

ChangeLog: https://github.com/BuddiesOfBudgie/budgie-desktop/releases/tag/v10.8

Budgie 10.8 is a brand new release series for Budgie Desktop, featuring
improvements to Budgie Menu, adoption of StatusNotifier support in System Tray,
Magpie v0.x support, and more!

PR: 273269
Reported by: duchateau.olivier@gmail.com (maintainer)