Fix page size error. (#4401)

### What problem does this PR solve?

#4400

### Type of change

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

rag/nlp/search.py

                               "count": v["count"]} for k,
                              v in sorted(ranks["doc_aggs"].items(),
                                          key=lambda x:x[1]["count"] * -1)]
+        ranks["chunks"] = ranks["chunks"][:page_size]
 
         return ranks