DOCS: Fixes broken GitHub badge (#3438)

Author: cafferata

README.md

@@ -1,6 +1,6 @@
 # DNSControl
 
-[![StackExchange/dnscontrol/build](https://github.com/StackExchange/dnscontrol/actions/workflows/pr_test.yml/badge.svg)](https://github.com/StackExchange/dnscontrol/actions/workflows/pr_test.yml)
+[![StackExchange/dnscontrol/build](https://github.com/StackExchange/dnscontrol/actions/workflows/pr_build.yml/badge.svg)](https://github.com/StackExchange/dnscontrol/actions/workflows/pr_build.yml)
 [![Google Group](https://img.shields.io/badge/google%20group-chat-green.svg)](https://groups.google.com/forum/#!forum/dnscontrol-discuss)
 [![PkgGoDev](https://pkg.go.dev/badge/github.com/StackExchange/dnscontrol)](https://pkg.go.dev/github.com/StackExchange/dnscontrol/v4)