Fix CI shield

Author: dcherian

README.md

@@ -1,4 +1,4 @@
-[![GitHub Workflow CI Status](https://img.shields.io/github/workflow/status/xarray-contrib/flox/CI?logo=github&style=flat)](https://github.com/xarray-contrib/flox/actions)
+[![GitHub Workflow CI Status](https://img.shields.io/github/actions/workflow/status/xarray-contrib/flox/ci.yaml?branch=main&logo=github&style=flat)](https://github.com/xarray-contrib/flox/actions)
 [![pre-commit.ci status](https://results.pre-commit.ci/badge/github/xarray-contrib/flox/main.svg)](https://results.pre-commit.ci/latest/github/xarray-contrib/flox/main)
 [![image](https://img.shields.io/codecov/c/github/xarray-contrib/flox.svg?style=flat)](https://codecov.io/gh/xarray-contrib/flox)
 [![Documentation Status](https://readthedocs.org/projects/flox/badge/?version=latest)](https://flox.readthedocs.io/en/latest/?badge=latest)