Fix GitHub actions badge in README

Author: odow

README.md

@@ -2,7 +2,7 @@
 
 [![stable docs](https://img.shields.io/badge/docs-stable-blue.svg)](https://jump.dev/DiffOpt.jl/stable)
 [![development docs](https://img.shields.io/badge/docs-dev-blue.svg)](https://jump.dev/DiffOpt.jl/dev)
-[![Build Status](https://github.com/jump-dev/DiffOpt.jl/workflows/CI/badge.svg?branch=master)](https://github.com/jump-dev/DiffOpt.jl/actions?query=workflow%3ACI)
+[![Build Status](https://github.com/jump-dev/DiffOpt.jl/actions/workflows/ci.yml/badge.svg?branch=master)](https://github.com/jump-dev/DiffOpt.jl/actions?query=workflow%3ACI)
 [![Coverage](https://codecov.io/gh/jump-dev/DiffOpt.jl/branch/master/graph/badge.svg)](https://codecov.io/gh/jump-dev/DiffOpt.jl)
 
 [DiffOpt.jl](https://github.com/jump-dev/DiffOpt.jl) is a package for