Fail fast example doesn't show how to fail fast!

[ldionne]

The text says:

To automatically cancel any remaining jobs as soon as the first job fails (except jobs that you've marked as soft_fail), add the cancel_on_build_failing: true attribute to your command steps.

But then the example that follows never uses cancel_on_build_failing!

Seen here: https://buildkite.com/docs/pipelines/command-step#fail-fast