[FLINK-20906][legal] Update copyright year to 2021 for NOTICE files.

This closes #14598
diff --git a/flink-connectors/flink-sql-connector-elasticsearch6/src/main/resources/META-INF/NOTICE b/flink-connectors/flink-sql-connector-elasticsearch6/src/main/resources/META-INF/NOTICE
index b77afb5..b8f64c2 100644
--- a/flink-connectors/flink-sql-connector-elasticsearch6/src/main/resources/META-INF/NOTICE
+++ b/flink-connectors/flink-sql-connector-elasticsearch6/src/main/resources/META-INF/NOTICE
@@ -1,5 +1,5 @@
 flink-sql-connector-elasticsearch6
-Copyright 2014-2020 The Apache Software Foundation
+Copyright 2014-2021 The Apache Software Foundation
 
 This product includes software developed at
 The Apache Software Foundation (http://www.apache.org/).
diff --git a/flink-connectors/flink-sql-connector-elasticsearch7/src/main/resources/META-INF/NOTICE b/flink-connectors/flink-sql-connector-elasticsearch7/src/main/resources/META-INF/NOTICE
index 5a8708e..f6ebf8b 100644
--- a/flink-connectors/flink-sql-connector-elasticsearch7/src/main/resources/META-INF/NOTICE
+++ b/flink-connectors/flink-sql-connector-elasticsearch7/src/main/resources/META-INF/NOTICE
@@ -1,5 +1,5 @@
 flink-sql-connector-elasticsearch7
-Copyright 2014-2020 The Apache Software Foundation
+Copyright 2014-2021 The Apache Software Foundation
 
 This product includes software developed at
 The Apache Software Foundation (http://www.apache.org/).