Update handler.rs Copyright header for 2021
This file was modified in 2021, so update the copyright
headers accordingly.
/*
* Copyright 2017 Bitwise IO, Inc.
- * Copyright 2019 Cargill Incorporated
+ * Copyright 2019-2021 Cargill Incorporated
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
