Create compatibility documentation for kubernetes versions

Created by: caugustus-sourcegraph

Do we have any documentation / guidance with respect to kubernetes cluster upgrade and sourcegraph? https://sourcegraph.slack.com/archives/C02E4HE42BX/p1651746268445069

We should add some basic guidance to the upgrade docs and note any compatibility issues. For instance, in Kubernetes version 1.22, the networking.k8s.io/v1beta1 api was removed. The deployment manifests were updated to remove this API reference as of the Sourcegraph 3.35 release.