main/postmarketos-ui-gnome: add dep on gnome-shell (MR 3443)

Since merging the gnome shell on mobile MR 3404, gnome-shell needs to be
explicitly installed or else it gets removed on upgrade.

[ci:skip-build]: already built successfully in CI

main/postmarketos-ui-gnome/APKBUILD

@@ -2,7 +2,7 @@
 # Maintainer: Martijn Braam <martijn@brixit.nl>
 pkgname=postmarketos-ui-gnome
 pkgver=3
-pkgrel=1
+pkgrel=2
 pkgdesc="(Wayland) Gnome Shell"
 url="https://gnome.org/"
 arch="noarch"
@@ -10,9 +10,10 @@ license="GPL-3.0-or-later"
 depends="
 	gdm
 	gnome
+	gnome-shell
 	kgx
-	postmarketos-base-ui-gnome
 	postmarketos-artwork-wallpapers
+	postmarketos-base-ui-gnome
 	xwayland
 	"
 install="$pkgname.post-install $pkgname.post-upgrade"