Remove the postmarketos-base-ui-gnome-wallpapers subpackage that only
Phosh and GNOME desktop used to depend on, and instead add a hard
dependency on postmarketos-artwork-wallpapers.
The config that enables the wallpapers will be moved to
postmarketos-artwork-wallpapers in the next commit. This will make it
easier to maintain, the paths to the wallpapers will only be in one
package instead of being scattered across many.
These apps are useful to have on the full GNOME desktop too, and this
removes the need to duplicate package lists across UI meta packages that
depend on the base gnome UI package.
See previous commit for rationale.
[ci:skip-vercheck]: No need to increment pkgrel when only changing
_pmb_recommends.
[ci:skip-build]: already built successfully in CI
xdg-desktop-portal-gnome is needed for example for mime type associations.
Without it, the default gnome based shell installations couldn't detect which
mime types were provided by which applications, xdg-open and the
Default Applications tab in GNOME Control Center didn't work.
This dependency was missing from postmarketos-ui-phosh, so let's add it
and xdg-user-dirs to postmarketos-base-ui-gnome to make sure it's not repeated
in every gnome based UI.
