Chore: update readme Dingtalk QR code

Author: iamkun

README.md

@@ -237,7 +237,7 @@ Become a sponsor and get your logo on our README on Github with a link to your s
 
 Scan the QR code using [Dingtalk App](https://www.dingtalk.com/) to join in discussion group :
 
-<img alt="Join Discusion Group" src="https://user-images.githubusercontent.com/17680888/60150281-95183f80-980a-11e9-88a8-d324c5e8d83b.png" width="300">
+<img alt="Join Discusion Group" src="https://user-images.githubusercontent.com/17680888/66537329-9a4b9100-eb52-11e9-9d99-65469cfdae58.jpeg" width="300">
 
 
 ## LICENSE