API doc: Correct Base URL and Dataset URL. (#1444)

The correct URL is http://<host_address>/v1/api , not
http://<host_address>/api/v1 .

### What problem does this PR solve?

### Type of change

- [x] Documentation Update

---------

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

docs/references/ragflow_api.md

@@ -8,7 +8,7 @@ RAGFlow offers RESTful APIs for you to integrate its capabilities into third-par
 
 ## Base URL
 ```
-http://<host_address>/api/v1/
+http://<host_address>/v1/api/
 ```
 
 ## Dataset URL