message: fix gcp zone example value which used invalid naming pattern
diff: @@ -30,7 +30,7 @@ After cloning this repo, `cd` into it and run these commands. A GKE Kubernetes c
  ```bash
  $ pulumi config set gcp:project [your-gcp-project-here]
  - $ pulumi config set gcp:zone us-west-1a # any valid GCP zone here
  + $ pulumi config set gcp:zone us-west1-a # any valid GCP zone here
  $ pulumi config set password --secret [your-cluster-password-here]
  ```
  