Remove gitter from readme as it is dead

Author: fliiiix

README.md

@@ -6,7 +6,6 @@
 ***
 
 [![PyPI License](https://img.shields.io/pypi/l/radish-bdd.svg)](https://github.com/radish-bdd/radish/blob/master/LICENSE)
-[![Gitter](https://badges.gitter.im/radish-bdd/radish.svg)](https://gitter.im/radish-bdd/radish?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
 <br>
 [![Actions Status](https://github.com/radish-bdd/radish/workflows/CI/badge.svg)](https://github.com/radish-bdd/radish/actions?branch=stable)
 [![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/ambv/black)