Fix badge in README

See <badges/shields#8671>.

README.md

@@ -1,6 +1,6 @@
 # bore
 
-[![Build status](https://img.shields.io/github/workflow/status/ekzhang/bore/CI)](https://github.com/ekzhang/bore/actions)
+[![Build status](https://img.shields.io/github/actions/workflow/status/ekzhang/bore/ci.yml)](https://github.com/ekzhang/bore/actions)
 [![Crates.io](https://img.shields.io/crates/v/bore-cli.svg)](https://crates.io/crates/bore-cli)
 
 A modern, simple TCP tunnel in Rust that exposes local ports to a remote server, bypassing standard NAT connection firewalls. **That's all it does: no more, and no less.**