lorax: make sure qubes-artwork is installed

DNF based pungi isn't deterministic and sometimes chooses fedora-logos
(both provide system-logos). Make sure the right one is installed.

QubesOS/qubes-issues#1807

lorax-templates-qubes/templates/runtime-install.tmpl

@@ -137,6 +137,7 @@ installpkg gnome-icon-theme-legacy
 installpkg aajohan-comfortaa-fonts
 installpkg abattis-cantarell-fonts
 installpkg sil-scheherazade-fonts
+installpkg qubes-artwork
 
 ## debugging/bug reporting tools
 installpkg gdb-gdbserver