Fix typo

Signed-off-by: Jael Gu <mengjia.gu@zilliz.com>

README.md

@@ -9,12 +9,12 @@ This operator uses reads the waveform of an audio file and then applies VGGish t
 ## Interface
 
 ```python
-__call__(self, filepath: str)
+__call__(self, audio_path: str)
 ```
 
 **Args:**
 
-- filepath:
+- audio_path:
   - the input audio path
   - supported types: str