doc: update produce api version info

Author: RunnningPig

README.md

@@ -282,7 +282,8 @@ producer config, most like in <http://kafka.apache.org/documentation.html#produc
 * `api_version`
 
     Specifies the produce API version. Default `0`.
-    If you use Kafka 0.10.0.0 or higher, `api_version` can use `0`, `1` or `2`.
+    If you use Kafka 4.0 or higher, `api_version` should be `3`.
+    If you use Kafka 0.10.0.0 up to 3.x, `api_version` can use `0`, `1` or `2`.
     If you use Kafka 0.9.x, `api_version` should be `0` or `1`.
     If you use Kafka 0.8.x, `api_version` should be `0`.