The _"Fleet's best practice `fleet-deployment.yml` file"_ link on the
["Deploy Fleet on Kubernetes" docs
page](https://fleetdm.com/docs/deploy/deploy-fleet-on-kubernetes)
doesn't actually target the YAML file it purports to and, instead, it
just points to the Markdown version of the "Deploy Fleet on Kubernetes"
docs on GitHub.
This PR changes the target URL so that link actually goes to the place
where one would expect it to (the YAML file).