docs: add ansible_pull_hosts to the desired minimum roles/groups

docs/create-new-web-service-vm.md

@@ -42,6 +42,7 @@ As the first step, we need to make the host known to Ansible.
        1. As a minimum, you'll want the following roles:
           - `base_config_hosts`
           - `infrastructure_authorized_keys_hosts`
+          - `ansible_pull_hosts`
        2. For a typical web service based on Docker Compose, you'll also want:
           - `docker_compose_hosts`
           - `nginx_hosts`