wallpapers: pmos.xml: point to the meadow wallpapers (MR 28)

This way they should be selectable in the UI instead of the old ones.
In the process also change the name, since these wallpapers are more
generic.

wallpapers/gnome/pmos.xml

@@ -2,9 +2,9 @@
 <!DOCTYPE wallpapers SYSTEM "gnome-wp-list.dtd">
 <wallpapers>
   <wallpaper deleted="false">
-    <name>postmarketOS GNOME Mobile</name>
-    <filename>/usr/share/wallpapers/postmarketos-gnome-light.jpg</filename>
-    <filename-dark>/usr/share/wallpapers/postmarketos-gnome-dark.jpg</filename-dark>
+    <name>postmarketOS Wallpapers</name>
+    <filename>/usr/share/wallpapers/meadow-light.jpg</filename>
+    <filename-dark>/usr/share/wallpapers/meadow-dark.jpg</filename-dark>
     <options>zoom</options>
     <shade_type>solid</shade_type>
     <pcolor>#73A82F</pcolor>