Update copyright for 2020.
diff --git a/NOTICE.txt b/NOTICE.txt
index c7499a1..17da355 100644
--- a/NOTICE.txt
+++ b/NOTICE.txt
@@ -1,5 +1,5 @@
 Apache HttpComponents Stylecheck Plugin Configuration
-Copyright 2013-2018 The Apache Software Foundation
+Copyright 2013-2020 The Apache Software Foundation
 
 This product includes software developed at
 The Apache Software Foundation (http://www.apache.org/).