main/postmarketos-ui-gnome: add two useful apps to recommends (MR 5077)

These are useful on desktops/laptops/tablets.

This was only added to the gnome (desktop) UI because:

1) The system monitor could be useful on mobile devices however the UI
   is not adaptive.

2) Disk utility isn't that useful on mobile devices since it tends to
   show dozens of partitions on android phones, and so it's kinda
   confusing and it would be easy for users to mess things up.

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

main/postmarketos-ui-gnome/APKBUILD

@@ -2,7 +2,7 @@
 # Maintainer: Oliver Smith <ollieparanoid@postmarketos.org>
 pkgname=postmarketos-ui-gnome
 pkgver=3
-pkgrel=8
+pkgrel=9
 pkgdesc="(Wayland) Gnome Shell"
 url="https://gnome.org/"
 # armhf blocked by gnome-shell -> gjs -> mozjs102
@@ -19,6 +19,8 @@ depends="
 	"
 _pmb_recommends="
 	gnome-calendar
+	gnome-disk-utility
+	gnome-system-monitor
 	nautilus
 	"
 install="$pkgname.post-install $pkgname.post-upgrade"