Specify main branch for coverage badge svg

Author: softwareengineerprogrammer

README.rst

@@ -56,7 +56,7 @@ Free software: `MIT license <LICENSE>`__
     :target: https://nrel.github.io/GEOPHIRES-X
     :alt: Documentation Status
 
-.. |coverage| image:: https://coveralls.io/repos/github/softwareengineerprogrammer/GEOPHIRES-X/badge.svg
+.. |coverage| image:: https://coveralls.io/repos/github/softwareengineerprogrammer/GEOPHIRES-X/badge.svg?branch=main
     :target: https://coveralls.io/github/softwareengineerprogrammer/GEOPHIRES-X?branch=main
     :alt: Coverage Status