MT#58381 Use short name for GPL-3 in debian/copyright

Change-Id: I3cc2fe5e911ca194655210b574053871b5631b72

debian/copyright

@@ -5,7 +5,7 @@ Upstream-Name: kamailio-config-tests
 Files: *
 Copyright:
  Copyright © 2013-2021 Sipwise GmbH, Austria
-License: GPL-3.0+
+License: GPL-3+
  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or