gluon-web-autopupdater: migrate to spdx license header

package/gluon-web-autoupdater/luasrc/lib/gluon/config-mode/model/admin/autoupdater.lua

---[[
-Copyright 2013 Nils Schneider <nils@nilsschneider.net>
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-        http://www.apache.org/licenses/LICENSE-2.0
-]]--
+-- SPDX-FileCopyrightText: 2013 Nils Schneider <nils@nilsschneider.net>
+-- SPDX-License-Identifier: Apache-2.0
 
 local uci = require("simple-uci").cursor()
 local autoupdater = uci:get_first("autoupdater", "autoupdater")