Use Regex for Copyright Year in Header Check (#1002)

diff --git a/portable/GCC/ATMega323/portmacro.h b/portable/GCC/ATMega323/portmacro.h
index 275468b..6ed5e42 100644
--- a/portable/GCC/ATMega323/portmacro.h
+++ b/portable/GCC/ATMega323/portmacro.h
@@ -1,6 +1,6 @@
 /*
  * FreeRTOS Kernel <DEVELOPMENT BRANCH>
- * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
+ * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
  *
  * SPDX-License-Identifier: MIT
  *