fix formatting of bootstrap token generation

docs/03-auth-configs.md

@@ -38,7 +38,9 @@ This section will walk you through the creation of a TLS bootstrap token that wi
 
 Generate a token:
 
+```
 BOOTSTRAP_TOKEN=$(head -c 16 /dev/urandom | od -An -t x | tr -d ' ')
+```
 
 Generate a token file:
 
@@ -135,4 +137,4 @@ kubectl config use-context default --kubeconfig=kube-proxy.kubeconfig
 for host in worker0 worker1 worker2; do
   gcloud compute copy-files bootstrap.kubeconfig kube-proxy.kubeconfig ${host}:~/
 done
-```
+```