fixed broken readthedocs link

README.md

@@ -5,7 +5,7 @@
 [![GitHub Repository](https://img.shields.io/github/repo-size/sambit-giri/tools21cm)](https://github.com/sambit-giri/tools21cm)
 [![CI status](https://github.com/sambit-giri/tools21cm/actions/workflows/ci.yml/badge.svg)](https://github.com/sambit-giri/tools21cm/actions/workflows/ci.yml)
 [![PyPI version](https://badge.fury.io/py/tools21cm.svg)](https://badge.fury.io/py/tools21cm)
-[![Read the Docs](https://readthedocs.org/projects/tools21cm/badge/?version=latest)](https://tools21cm.readthedocs.io/en/latest/)
+[![Read the Docs](https://readthedocs.org/projects/tools21cm/badge/?version=latest)](https://tools21cm.readthedocs.io/)
 
 A python package for analysing simulated 21-cm signals from the Epoch of Reionization (EoR) and Cosmic Dawn (CD). Full documentation (with examples, installation instructions and complete module description) can be found at [readthedocs](https://tools21cm.readthedocs.io/).