Small update on README.md

Author: erichorwath

tools/setup-envtest/README.md

@@ -11,7 +11,7 @@ module):
 go install sigs.k8s.io/controller-runtime/tools/setup-envtest@latest
 ```
 
-If you are using Golang 1.23, use the `release-0.19` branch instead:
+If you are using Golang 1.23, use the `release-0.20` branch instead:
 
 ```shell
 go install sigs.k8s.io/controller-runtime/tools/[email protected]