fix year in notice (#3647)

diff --git a/NOTICE b/NOTICE
index 5e058ca..7e3a0d2 100644
--- a/NOTICE
+++ b/NOTICE
@@ -1,5 +1,5 @@
 Apache Heron (Incubating)
-Copyright 2018-2019 The Apache Software Foundation
+Copyright 2018-2020 The Apache Software Foundation
 
 This product includes software developed at
 The Apache Software Foundation (http://www.apache.org/).