docs: caniusepython3.com is discontinued

Author: weakish

README.md

@@ -1,7 +1,6 @@
 # Python-SDK
 
 ![GitHub Workflow Status (branch)](https://img.shields.io/github/workflow/status/leancloud/python-sdk/Python%20package/master)
-[![Python3 Support](https://caniusepython3.com/project/leancloud-sdk.svg)](https://caniusepython3.com/project/leancloud-sdk)
 [![Codecov](https://img.shields.io/codecov/c/github/leancloud/python-sdk.svg)](https://codecov.io/gh/leancloud/python-sdk)
 
 LeanCloud Python SDK