Let Flatpak download all language files at once

Basically we'll set `flatpak config --set languages "*"` which should allow Flatpak to download every language pack available into the image. This should allow translated Flatpak apps on non-english systems.
Fixes #500

mkosi.extra/usr/lib/install-flatpaks

@@ -5,4 +5,3 @@
 set -eux
 
 flatpak install --noninteractive --assumeyes --sideload-repo=/usr/share/factory/var/lib/flatpak/.ostree/repo org.gtk.Gtk3theme.Breeze org.kde.gwenview org.kde.okular org.kde.kwrite org.kde.haruna org.kde.qrca org.kde.ark org.kde.kcalc org.mozilla.firefox
-flatpak repair # Get localizations back now

mkosi.postinst.chroot

@@ -70,8 +70,8 @@ download_flatpaks() {
     # Do this separately, when used as part of remote-add it complains about GPG for unknown reasons
     flatpak remote-modify --collection-id=org.flathub.Stable flathub
 
-    # Only check out en. We don't really support other languages on the live image at this time.
-    flatpak config --set languages en
+    # Setting "*" will let Flatpak download all languages at once
+    flatpak config --set languages "*"
 
     kde_nightly=(
         ark