refactor: 优化RestTemplate在低版本引起的一个I/O异常

详细可参考：https://github.com/spring-projects/spring-framework/issues/21321

payment-spring-boot-autoconfigure/src/main/java/cn/felord/payment/wechat/v2/WechatV2Client.java

@@ -48,9 +48,4 @@ public class WechatV2Client {
     public WechatMetaBean getWechatMetaBean() {
         return wechatMetaBean;
     }
-
-
-    public static void main(String[] args) {
-        System.out.println("hello 2021");
-    }
 }