[PRQ#38307] Merge Request for syncthing-gtk-python3

Salamandar [1] filed a request to merge syncthing-gtk-python3 [2] into syncthing-gtk [3]: This new package uses a communautary maintained repository instead of one of the multiple forks owned by one person only. This new repository is obviously python3, so we're dropping the suffix. [1] https://aur.archlinux.org/account/Salamandar/ [2] https://aur.archlinux.org/pkgbase/syncthing-gtk-python3/ [3] https://aur.archlinux.org/pkgbase/syncthing-gtk/