Fix: add file convert backward compatibility (#14583)

### What problem does this PR solve?

add file convert backward compatibility

### Type of change

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

docs/references/http_api_reference.md

@@ -7430,6 +7430,10 @@ or
 ```bash
 curl --request POST \
      --url http://{address}/api/v1/files/link-to-datasets \
+     --header 'Content-Type: application/json' \
+     --header 'Authorization: Bearer <YOUR_API_KEY>' \
+     --data '{
+          "file_ids": ["file_id_1", "file_id_2"],
           "kb_ids": ["dataset_id_1", "dataset_id_2"]
      }'
 ```