gluon-core: remove unused gluon.sysctl Lua module

package/gluon-core/luasrc/usr/lib/lua/gluon/sysctl.lua

-local util = require 'gluon.util'
-
-
-module 'gluon.sysctl'
-
-function set(name, value)
-	local new
-	if value then
-		new = name .. '=' .. value .. '\n'
-	end
-	util.replace_prefix('/etc/sysctl.conf', name .. '=', new)
-end