Update libmpdec license dates (GH-21216)
diff --git a/Doc/license.rst b/Doc/license.rst
index 472a5cf..fa6d71a 100644
--- a/Doc/license.rst
+++ b/Doc/license.rst
@@ -889,7 +889,7 @@
The :mod:`_decimal` module is built using an included copy of the libmpdec
library unless the build is configured ``--with-system-libmpdec``::
- Copyright (c) 2008-2016 Stefan Krah. All rights reserved.
+ Copyright (c) 2008-2020 Stefan Krah. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions