Fix CI badge in README.md (#231)

Author: odow

README.md

@@ -2,7 +2,7 @@
 
 # Cbc.jl
 
-[![Build Status](https://github.com/jump-dev/Cbc.jl/workflows/CI/badge.svg?branch=master)](https://github.com/jump-dev/Cbc.jl/actions?query=workflow%3ACI)
+[![Build Status](https://github.com/jump-dev/Cbc.jl/actions/workflows/ci.yml/badge.svg?branch=master)](https://github.com/jump-dev/Cbc.jl/actions?query=workflow%3ACI)
 [![codecov](https://codecov.io/gh/jump-dev/Cbc.jl/branch/master/graph/badge.svg)](https://codecov.io/gh/jump-dev/Cbc.jl)
 
 [Cbc.jl](https://github.com/jump-dev/Cbc.jl) is a wrapper for the [COIN-OR Branch and Cut (Cbc)](https://projects.coin-or.org/Cbc)