add more desc about replicatuin-factor (#15068) (#15078)

ticdc/ticdc-sink-to-kafka.md

@@ -56,7 +56,7 @@ The following are descriptions of sink URI parameters and values that can be con
 | `kafka-client-id`    | Specifies the Kafka client ID of the replication task (optional. `TiCDC_sarama_producer_replication ID` by default). |
 | `partition-num`      | The number of the downstream Kafka partitions (optional. The value must be **no greater than** the actual number of partitions; otherwise, the replication task cannot be created successfully. `3` by default). |
 | `max-message-bytes`  | The maximum size of data that is sent to Kafka broker each time (optional, `10MB` by default). From v5.0.6 and v4.0.6, the default value has changed from `64MB` and `256MB` to `10MB`. |
-| `replication-factor` | The number of Kafka message replicas that can be saved (optional, `1` by default).                       |
+| `replication-factor` | The number of Kafka message replicas that can be saved (optional, `1` by default). This value must be greater than or equal to the value of [`min.insync.replicas`](https://kafka.apache.org/33/documentation.html#brokerconfigs_min.insync.replicas) in Kafka. |
 | `required-acks` | A parameter used in the `Produce` request, which notifies the broker of the number of replica acknowledgements it needs to receive before responding. Value options are `0` (`NoResponse`: no response, only `TCP ACK` is provided), `1` (`WaitForLocal`: responds only after local commits are submitted successfully), and `-1` (`WaitForAll`: responds after all replicated replicas are committed successfully. You can configure the minimum number of replicated replicas using the [`min.insync.replicas`](https://kafka.apache.org/33/documentation.html#brokerconfigs_min.insync.replicas) configuration item of the broker). (Optional, the default value is `-1`).    |
 | `compression` | The compression algorithm used when sending messages (value options are `none`, `lz4`, `gzip`, `snappy`, and `zstd`; `none` by default). |
 | `protocol` | The protocol with which messages are output to Kafka. The value options are `canal-json`, `open-protocol`, `canal`, `avro` and `maxwell`.   |