refactor: no need to inherit in python3 clean the code (#5659)

### What problem does this PR solve?

As title

### Type of change


- [x] Refactoring

Signed-off-by: yihong0618 <zouzou0208@gmail.com>

rag/utils/minio_conn.py

@@ -24,7 +24,7 @@ from rag.utils import singleton
 
 
 @singleton
-class RAGFlowMinio(object):
+class RAGFlowMinio:
     def __init__(self):
         self.conn = None
         self.__open__()