doc: update copyright for standards.perl

It was missing "(C)", so gnulib update-copyright missed it.

diff --git a/Documentation/standards.perl b/Documentation/standards.perl
index 10b16140cd4e1a6876ef94ef855db5b5f4c8f0eb..2c30cbb9ce19a821f1fb345872f6ac29a06737a8 100755 (executable)
--- a/Documentation/standards.perl
+++ b/Documentation/standards.perl
@@ -72,6 +72,6 @@ Other relevant documentation
 Copyright
 ---------
 
 Copyright
 ---------
 

-Copyright 2019 all contributors <meta@public-inbox.org>
+Copyright (C) 2019-2020 all contributors <meta@public-inbox.org>

 License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 EOF
 License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 EOF