doc: kill disused codecov badge

Author: agriffis

README.rst

@@ -174,8 +174,6 @@ Released under the `MIT license <https://github.com/scampersand/envbash-python/b
 .. |Build Status| image:: https://img.shields.io/github/actions/workflow/status/scampersand/envbash-python/test.yml?branch=master&style=plastic
    :target: https://github.com/scampersand/envbash-python/actions/workflows/test.yml
 
-.. |Coverage Report| image:: https://img.shields.io/codecov/c/github/scampersand/envbash-python/master.svg?style=plastic
-   :target: https://codecov.io/gh/scampersand/envbash-python/branch/master
 
 .. |PyPI| image:: https://img.shields.io/pypi/v/envbash.svg?style=plastic
    :target: PyPI_