Certain keywords have been deprecated in upstream Alertmanager v 0.22.0.

OCP 4.9 updated the Alertmanager version to 0.22.2, and the OCP 4.9+ documentation does not make a note of these deprecations for customers who use these keywords.

We need to update these versions of the docs to mention the deprecated Alertmanager keywords.

For a list of deprecated keywords for Prometheus config settings, see the upstream Prometheus docs: https://prometheus.io/docs/alerting/latest/configuration/

Reported by a customer about Alertmanager route keywords per this Slack thread: https://redhat-internal.slack.com/archives/C0VMT03S5/p1673593403276959