Update codecov link (#271)

README.md

@@ -1,7 +1,7 @@
 [![Binder](https://mybinder.org/badge_logo.svg)](https://mybinder.org/v2/gh/jupyter/nbclient/main?filepath=binder%2Frun_nbclient.ipynb)
 [![Build Status](https://github.com/jupyter/nbclient/workflows/CI/badge.svg)](https://github.com/jupyter/nbclient/actions)
 [![Documentation Status](https://readthedocs.org/projects/nbclient/badge/?version=latest)](https://nbclient.readthedocs.io/en/latest/?badge=latest)
-[![image](https://codecov.io/github/jupyter/nbclient/coverage.svg?branch=main)](https://codecov.io/github/jupyter/nbclient?branch=main)
+[![CodeCov](https://codecov.io/gh/jupyter/nbclient/coverage.svg?branch=main)](https://codecov.io/gh/jupyter/nbclient?branch=main)
 [![Python 3.7](https://img.shields.io/badge/python-3.7-blue.svg)](https://www.python.org/downloads/release/python-370/)
 [![Python 3.8](https://img.shields.io/badge/python-3.8-blue.svg)](https://www.python.org/downloads/release/python-380/)
 [![Python 3.9](https://img.shields.io/badge/python-3.9-blue.svg)](https://www.python.org/downloads/release/python-390/)

docs/index.rst

@@ -9,7 +9,7 @@ Welcome to nbclient
  :target: https://github.com/jupyter/nbclient/actions
 .. image:: https://codecov.io/github/jupyter/nbclient/coverage.svg?branch=master
  :alt: CodeCov
- :target: https://codecov.io/github/jupyter/nbclient
+ :target: https://codecov.io/gh/jupyter/nbclient
 
 ---