Fix: aliyun oss need to use s3 signature_version (#12766)

### What problem does this PR solve?

Aliyun OSS do not support boto s4 signature_version which will lead to
an error:

```
botocore.exceptions.ClientError: An error occurred (InvalidArgument) when calling the PutObject operation: aws-chunked encoding is not supported with the specified x-amz-content-sha256 value
```

According to aliyun oss docs, oss_conn need to use s3 signature_version.

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

docker/.env

@@ -227,6 +227,7 @@ EMBEDDING_BATCH_SIZE=${EMBEDDING_BATCH_SIZE:-16}
 # ENDPOINT=http://oss-cn-hangzhou.aliyuncs.com
 # REGION=cn-hangzhou
 # BUCKET=ragflow65536
+# 
 
 # A user registration switch:
 # - Enable registration: 1