docs: Add note to 1.22 about the CA CN rename (#15324)

* docs(release): add note to 1.22 about the CA CN rename

- this broke some of my teams' automation code that relied on the CN,
  so thought it would be good to call out in case anyone else stumbles
  upon this in order to not spend a few hours debugging
  - this change may particularly impact Prod environments, where the
    cluster has not been rebuilt in some time (years), and so they will
    have the old CN while new clusters in lower environments will have
    the new CN
    - so code that relies on the CN may unexpectedly break Production
      while working fine in lower environments
      - fortunately we caught this in our QA env, but it passed Dev fine

* Apply suggestion from @hakman

---------

Co-authored-by: Ciprian Hacman <[email protected]>

Author: agilgur5

docs/releases/1.22-NOTES.md

@@ -163,6 +163,8 @@ For file assets, it means adding an explicit path as shown below:
   The previous behavior of using self-signed certs may be restored by setting `kubeControllerManager.tlsCertFile` and/or
   `kubeScheduler.tlsCertFile` to `""` in the cluster spec.
 
+* kOps has changed the CN of the Kubernetes general CA from `kubernetes` to `kubernetes-ca`. This change is backward-compatible, but any tools using the CN will need to be updated.
+
 * Cilium now supports the wireguard protocol for transparent encryption.