cmake OpenBSD copyright notice correction

Brad Smith made this OpenBSD file based of the
FreeBSD cmake directives in commit ab58904
by the Monty Program Ab.

As such the Oracle Copyright header isn't really applicable.

cmake/os/OpenBSD.cmake

@@ -1,5 +1,4 @@
-
-# Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
+# Copyright (C) 2012 Monty Program Ab, 2021 Brad Smith
 # 
 # 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