User group QR code_update (#2422)

README.md

@@ -342,7 +342,7 @@ With authors' permission, we listed a set of NNI usage examples and relevant art
 Join IM discussion groups:
 |Gitter||WeChat|
 |----|----|----|
-|![image](https://user-images.githubusercontent.com/39592018/80665738-e0574a80-8acc-11ea-91bc-0836dc4cbf89.png)| OR |![image](https://github.com/JSong-Jia/NNI-user-group/blob/master/NNI%20user%20group_3.png)|
+|![image](https://user-images.githubusercontent.com/39592018/80665738-e0574a80-8acc-11ea-91bc-0836dc4cbf89.png)| OR |![image](https://github.com/JSong-Jia/NNI-user-group/blob/master/user%20group%20code_0512.jpg)|
 
 
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