Fix CI badge in README.md

The badge URL has changed, see https://github.com/badges/shields/issues/8671

README.md

@@ -1,7 +1,7 @@
 # Slither, the Solidity source analyzer
 <img src="./logo.png" alt="Logo" width="500"/>
 
-[![Build Status](https://img.shields.io/github/workflow/status/crytic/slither/CI/master)](https://github.com/crytic/slither/actions?query=workflow%3ACI)
+[![Build Status](https://img.shields.io/github/actions/workflow/status/crytic/slither/ci.yml?branch=master)](https://github.com/crytic/slither/actions?query=workflow%3ACI)
 [![Slack Status](https://empireslacking.herokuapp.com/badge.svg)](https://empireslacking.herokuapp.com)
 [![PyPI version](https://badge.fury.io/py/slither-analyzer.svg)](https://badge.fury.io/py/slither-analyzer)