remove go report card

Author: taowen

README.md

@@ -1,6 +1,5 @@
 [![Build Status](https://travis-ci.org/json-iterator/java.svg?branch=master)](https://travis-ci.org/json-iterator/java)
 [![codecov](https://codecov.io/gh/json-iterator/java/branch/master/graph/badge.svg)](https://codecov.io/gh/json-iterator/java)
-[![rcard](https://goreportcard.com/badge/github.com/json-iterator/java)](https://goreportcard.com/report/github.com/json-iterator/java)
 [![License](http://img.shields.io/badge/license-mit-blue.svg?style=flat-square)](https://raw.githubusercontent.com/json-iterator/java/master/LICENSE)
 [![Gitter chat](https://badges.gitter.im/gitterHQ/gitter.png)](https://gitter.im/json-iterator/Lobby)