Revert "Trebuchet: add default wallpaper"

Default Wallpapers should be handled by the overlay at
/device/qcom/common/device/overlay/packages/apps/Trebuchet/res/drawable-xhdpi/

This reverts commit d18f58a6.

Change-Id: If55848ac20351f24d3f228071f9af22fa0e9f675

WallpaperPicker/res/values-nodpi/wallpapers.xml

@@ -19,7 +19,6 @@
     <string-array name="wallpapers" translatable="false">
         <!-- This special drawable references the platform's private
              default_wallpaper resource so the user can always choose it. -->
-        <item>qti_default_wallpaper</item>
         <item>default_wallpaper</item>
 
         <!-- If you want additional bitmap drawable resources to appear in the