Incorrect cloud provider type for OpenStack terraform template

[a-anokhin]

https://github.com/Mirantis/launchpad/blob/ca0e887751bc3fe56a969dd26c59a1c48bf0279a/examples/terraform/openstack/output.tf#L62-L65

openstack is unsupported cloud provider type. Tested with launchpad 1.5.2 and receive error level=error msg="invalid Kubernetes config: cloud provider value must be one of [aws azure vsphere gce external]

For OpenStack provider should be external

cloud = {
    provider = "external"
    configFile = var.provider_config_file_path
}