add the note for offline asr, test=doc

demos/streaming_asr_server/README_cn.md

@@ -197,7 +197,6 @@ wget -c https://paddlespeech.bj.bcebos.com/PaddleAudio/zh.wav
 **注意：** 初次使用客户端时响应时间会略长
 - 命令行 (推荐使用)
    ```
-   # 使用 paddlespecch_asr 需要指定传入协议为 websocket
    paddlespeech_client asr_online --server_ip 127.0.0.1 --port 8090 --input ./zh.wav
    ```
 

paddlespeech/server/bin/paddlespeech_client.py

@@ -370,6 +370,8 @@ class ASRClientExecutor(BaseExecutor):
             str: The ASR results
         """
         # we use the asr server to recognize the audio text content
+        # and paddlespeech_client asr only support http protocol
+        protocol = "http"
         if protocol.lower() == "http":
             from paddlespeech.server.utils.audio_handler import ASRHttpHandler
             logger.info("asr http client start")