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/s3_conn.py

@@ -23,7 +23,7 @@ from rag.utils import singleton
 from rag import settings
 
 @singleton
-class RAGFlowS3(object):
+class RAGFlowS3:
     def __init__(self):
         self.conn = None
         self.s3_config = settings.S3