Corrected grammar

README.rst

@@ -212,7 +212,7 @@ Periodically you should update conda and the required Python packages. With the
     $ conda update conda
     $ conda env update -f conda_env.yml
 
-All Thanks To Our Contributors ✨🔗
-===================================
+Thanks To Our Contributors ✨🔗
+==========================
 .. image:: https://contrib.rocks/image?repo=gprMax/gprMax
    :target: https://github.com/gprMax/gprMax/graphs/contributors