fff-batman-adv: Remove vis_mode from uci config

According to the upstream repo, vis_mode has been removed since
batman-adv 2014.0.0.

See openwrt-routing/packages 8a66ed1.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
Reviewed-by: Robert Langhammer <rlanghammer@web.de>
Reviewed-by: Fabian Bläse <fabian@blaese.de>

src/packages/fff/fff-batman-adv/files/etc/uci-defaults/93-fff-batman-adv

@@ -12,7 +12,6 @@ uci batch <<EOF
   set batman-adv.bat0.bonding='0'
   set batman-adv.bat0.fragmentation='1'
   set batman-adv.bat0.orig_interval='1000'
-  set batman-adv.bat0.vis_mode='0'
   set batman-adv.bat0.distributed_arp_table='1'
   set batman-adv.bat0.hop_penalty='30'
 EOF