templates/boot/grub/addons.cfg: drop duplicate Netboot.xyz for non-efi

This boot menu entry is already present as "Netboot.xyz" in the lines
above.

Thanks to Chris for spotting this!

templates/boot/grub/addons.cfg

@@ -71,10 +71,4 @@ menuentry "Netboot.xyz" {
     fi
 }
 
-if [ "${grub_platform}" != "efi" ] ; then
-    menuentry "Netboot.xyz" {
-        insmod linux16
-        linux16 /boot/addons/netboot.xyz.lkrn
-    }
-fi # efi mode
 }