Feat: Why can't Retrieval component support internet web search. #5973 (#5978)

### What problem does this PR solve?

Feat: Why can't Retrieval component support internet web search. #5973

### Type of change


- [x] New Feature (non-breaking change which adds functionality)

web/src/pages/flow/constant.tsx

@@ -397,6 +397,7 @@ export const initialRetrievalValues = {
   similarity_threshold: 0.2,
   keywords_similarity_weight: 0.3,
   top_n: 8,
+  use_kg: false,
   ...initialQueryBaseValues,
 };