Update deprecation notice

- Remove "and the features that rely on it".
- Add link to blog post

Changelog: changed

data/deprecations/14-5-certificate-based-integration-with-kubernetes.yml

 - name: "Certificate-based integration with Kubernetes"
-  announcement_milestone: "14.5" # MIGHT CHANGE IF WE RELEASE THE ANNOUNCEMENT BLOG POST BEFORE THE 22ND
+  announcement_milestone: "14.5"
   announcement_date: "2021-11-15"
   removal_milestone: "15.0"
   body: |
-    We are deprecating the certificate-based integration with Kubernetes and the features that rely on it.
+    [We are deprecating the certificate-based integration with Kubernetes](https://about.gitlab.com/blog/2021/11/15/deprecating-the-cert-based-kubernetes-integration/).
     The timeline of removal of the integration from the product is not yet planned and we will communicate
     more details as they emerge. The certificate-based integration will continue to receive security and
     critical fixes, and features built on the integration will continue to work with supported Kubernetes

doc/update/deprecations.md

@@ -78,7 +78,7 @@ Announced: 2021-09-22
 
 ### Certificate-based integration with Kubernetes
 
-We are deprecating the certificate-based integration with Kubernetes and the features that rely on it.
+[We are deprecating the certificate-based integration with Kubernetes](https://about.gitlab.com/blog/2021/11/15/deprecating-the-cert-based-kubernetes-integration/).
 The timeline of removal of the integration from the product is not yet planned and we will communicate
 more details as they emerge. The certificate-based integration will continue to receive security and
 critical fixes, and features built on the integration will continue to work with supported Kubernetes