deskutils/syncthingtray: Update to 1.7.6
https://github.com/Martchus/syncthingtray/releases/tag/v1.7.3
https://github.com/Martchus/syncthingtray/releases/tag/v1.7.4
https://github.com/Martchus/syncthingtray/releases/tag/v1.7.5
https://github.com/Martchus/syncthingtray/releases/tag/v1.7.6
While here:
- Update WWW
- Switch to qt6 flavor by default
PR: 285374