Clean up contrib/

contrib/checkpoints.pl

@@ -1,6 +1,8 @@
 #!/usr/bin/perl
 # Copyright 2019-2020 The Hush developers
-# Released under the GPLv3
+# Copyright (c) 2019-2020 The Hush developers
+# Distributed under the GPLv3 software license, see the accompanying
+# file COPYING or https://www.gnu.org/licenses/gpl-3.0.en.html
 use warnings;
 use strict;
 # Generate checkpoint data for use in src/main.cpp