Fix for updating search vectors on edit (#3382)

Close #3377

backend/oasst_backend/prompt_repository.py

@@ -356,6 +356,7 @@ def revise_message(self, message_id: UUID, new_content: str):
         updated_message_data = {
             "payload": PayloadContainer(payload=db_payload.MessagePayload(text=new_content)),
             "edited": True,
+            "search_vector": None,
         }
 
         query = update(Message).where(Message.id == message_id).values(**updated_message_data)