DOC: Remove gitter badge

README.md

@@ -5,7 +5,6 @@
 Python interface to [PROJ](http://proj.org) (cartographic projections and coordinate transformations library).
 
 <p align="center">
-<a href="https://gitter.im/pyproj4-pyproj/community?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge"><img alt="Join the chat at https://gitter.im/pyproj4-pyproj/community" src="https://badges.gitter.im/pyproj4-pyproj/community.svg"></a>
 <a href="#contributors"><img alt="All Contributors" src="https://img.shields.io/badge/all_contributors-66-orange.svg?style=flat-square"></a>
 <a href="https://github.com/pyproj4/pyproj/actions?query=workflow%3ATests"><img alt="GitHub Actions Build Status" src="https://github.com/pyproj4/pyproj/workflows/Tests/badge.svg"></a>
 <a href="https://codecov.io/gh/pyproj4/pyproj"><img alt="Codecov Status" src="https://codecov.io/gh/pyproj4/pyproj/branch/main/graph/badge.svg"></a>