[doc] Hid new API doc on docusaurus site (#1198)

### What problem does this PR solve?

_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._

### Type of change
- [x] Documentation Update

docs/references/ragflow_api.md

@@ -1,3 +1,6 @@
+---
+sidebar_class_name: hidden
+---
 
 # API reference