Update OnionShare AppArmor profile (refs: #16914)

OnionShare fails to open the URL providing more information about
Stealth Onion Services. The added AppArmor rules allow executing
xdg-open and dependencies to fix this.

Edited by intrigeri:

 - Remove unnecessary permission to execute cut, head, awk, mawk, sed, tr, and
   xdg-mime.
 - Add missing permission to execute gio-launch-desktop.