Fix bug: broken import from rag.prompts.prompts (#10217)

### What problem does this PR solve?

Fix broken imports

### Type of change

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

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Signed-off-by: jinhai <haijin.chn@gmail.com>

api/db/services/conversation_service.py

@@ -23,7 +23,7 @@ from api.db.services.dialog_service import DialogService, chat
 from api.utils import get_uuid
 import json
 
-from rag.prompts import chunks_format
+from rag.prompts.generator import chunks_format
 
 
 class ConversationService(CommonService):