gnome3.dconf-editor: include gsettings_desktop_schemas

pkgs/desktops/gnome-3/3.24/core/dconf-editor/default.nix

···
   nativeBuildInputs = [ pkgconfig wrapGAppsHook ];
 
   buildInputs = [ vala_0_32 libxslt glib dbus_glib gnome3.gtk libxml2 gnome3.defaultIconTheme
+                  gnome3.gsettings_desktop_schemas
                   intltool docbook_xsl docbook_xsl_ns gnome3.dconf ];
 
   meta = with stdenv.lib; {