Update MHC annotation

We have renamed the annotation to machine.openshift.io/remediation-strategy: external-baremetal to reflect the possibility there might be other external remediation strategies in future. The reboot based external remediation strategy is currently focused on bare metal use cases. See also openshift/machine-api-operator#476

enhancements/machine-api/machine-health-checking.md

@@ -51,7 +51,8 @@ Reduce administrative overhead to run a cluster and ability to respond to failur
 
 - Providing administrator-defined short-circuiting of automated remediation when multiple nodes are unhealthy at the same time.
 
-- Allowing a new and custom remediation developed outside the machine-healthcheck controller and enable its use via annotation, e.g baremetal reboot.
+- Enable experimental remediation systems to be developed outside the machine-healthcheck controller via annotation, e.g baremetal reboot.
+  - If a strong need for multiple external remediation systems ever emerge a follow up proposal fleshing out stronger integration details must be provided for this to be supported as non-experimetal.
 
 
 ### Non-Goals
@@ -156,9 +157,9 @@ Out of band:
 
 ![Machine health check](./mhc.svg)
 
-#### Out of tree remediation controller, e.g baremetal reboot:
-- An external remediation can plug in by setting the `healthchecking.openshift.io/strategy: reboot` on the MHC resource.
-- An external remediation controller remediation could then watch machines annotated with `healthchecking.openshift.io/remediation: reboot` and react as it sees fit.
+#### Out of tree experimental remediation controller, e.g baremetal reboot:
+- An external remediation can plug in by setting the `machine.openshift.io/remediation-strategy` on the MHC resource.
+- An external remediation controller remediation could then watch machines annotated with `machine.openshift.io/remediation-strategy: external-baremetal` and react as it sees fit.
 
 ### Risks and Mitigations