refactor: V2退款进入过期模式

由于V3已经推出了退款功能，所以V2退款 WechatPayRefundApi 被标记为 Deprecated 未来会被移除

payment-spring-boot-autoconfigure/src/main/java/cn/felord/payment/wechat/v2/WechatPayRefundApi.java

@@ -28,6 +28,7 @@ import org.springframework.http.HttpMethod;
  * @author felord.cn
  * @since 1.0.5.RELEASE
  */
+@Deprecated
 public class WechatPayRefundApi {
     private final WechatV2Client wechatV2Client;