修改copyright

demos/sm3/sm3_hmac_demo.c

@@ -1,4 +1,12 @@
-#include <stdio.h>
+/*
+ *  Copyright 2022 The GmSSL Project. All Rights Reserved.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the License); you may
+ *  not use this file except in compliance with the License.
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ */
+
 #include <string.h>
 #include <stdlib.h>
 #include <gmssl/sm3.h>