gluon-core: fix removal of "OpenWrt" default WLAN interface

Fixes #534

package/gluon-core/files/lib/gluon/upgrade/200-wireless

@@ -7,8 +7,6 @@ local sysconfig = require 'gluon.sysconfig'
 
 -- Initial
 if not sysconfig.gluon_version then
-  local uci = require('luci.model.uci').cursor()
-
   uci:delete_all('wireless', 'wifi-iface')
 end