Update documentation reference from "Request Header v3" to "Request H…

…eader v2".

course-definition.yml

@@ -182,7 +182,7 @@ stages:
       | `client_id`           | NULLABLE_STRING | The client ID for the request             |
       | `tagged_fields`       | TAGGED_FIELDS   | Optional tagged fields                    |
 
-      The documentation for this can be found [here](https://kafka.apache.org/protocol.html#protocol_messages) under the "Request Header v3" section.
+      The documentation for this can be found [here](https://kafka.apache.org/protocol.html#protocol_messages) under the "Request Header v2" section.
 
       - `request_api_key`: An integer identifying the type of request.
         - The value of this field is different for each type of request.