Retrieval service optimization (#13849)

api/core/rag/datasource/retrieval_service.py

                                 DocumentSegment.id,
                                 DocumentSegment.content,
                                 DocumentSegment.answer,
-                                DocumentSegment.doc_metadata,
                             )
                         )
                         .first()
                     record = {
                         "segment": segment,
                         "score": document.metadata.get("score"),  # type: ignore
-                        "segment_metadata": segment.doc_metadata,
                     }
                     records.append(record)