We learnt through bug https://bugzilla.redhat.com/show_bug.cgi?id=1997404  that `machineconfiguration.openshift.io/ssh` annotation doesn't get reliably applied on node. This can cause confusion to our customer and reliability issue whoever depends on it.

Even without doing ssh to node, it is possible to update content of node using `oc debug node`. So, it makes sense to drop this annotation compared to keeping the current behavior.

Additional info: See https://coreos.slack.com/archives/C03C08UEJEB/p1652742194417789 where decision was made to drop this annotation

Acceptance Criteria:

• MCO completely drops writing `machineconfiguration.openshift.io/ssh` annotation
• Docs are updated accordingly