update year to 2021 in the NOTICE file.
diff --git a/NOTICE b/NOTICE
index 85e2dc3..086ee9f 100644
--- a/NOTICE
+++ b/NOTICE
@@ -1,5 +1,5 @@
 Apache RocketMQ
-Copyright 2016-2019 The Apache Software Foundation
+Copyright 2016-2021 The Apache Software Foundation
 
 This product includes software developed at
 The Apache Software Foundation (http://www.apache.org/).