KEP-1739: retro-update the customization with patches to Beta

The customization with patches graduated to Beta as part of the
the work in the KEP 970 (added in the kubeadm v1beta3 API) during
the 1.22 release cycle.

Retroactively update the KEP for customization with patches to Beta
as the related actions were completed.

Author: neolit123

keps/sig-cluster-lifecycle/kubeadm/1739-customization-with-patches/README.md

@@ -857,6 +857,8 @@ Major milestones might include
 
 - 2020-05-04: initial provisional KEP created
 - 2020-05-14: addressed feedback, filled PRR questionnaire, KEP marked as implementable
+- 2021-09-09: marked the feature as graduated to Beta. This was done as part of
+the kubeadm v1beta3 API work. The actions under "Alpha -> Beta" are completed.
 
 ## Drawbacks
 

keps/sig-cluster-lifecycle/kubeadm/1739-customization-with-patches/kep.yaml

@@ -18,15 +18,16 @@ replaces:
   - "/keps/sig-cluster-lifecycle/kubeadm/20190722-Advanced-configurations-with-kubeadm-(Kustomize).md"
 
 # The target maturity stage in the current dev cycle for this KEP.
-stage: alpha
+stage: beta
 
 # The most recent milestone for which work toward delivery of this KEP has been
 # done. This can be the current (upcoming) milestone, if it is being actively
 # worked on.
-latest-milestone: "v1.19"
+# NOTE: keeping this at v1.0 to avoid PRR. See milestones bellow.
+latest-milestone: "v1.0"
 
 # The milestone at which this feature was, or is targeted to be, at each stage.
 milestone:
   alpha: "v1.19"
-  beta: "v1.20"
-  stable: "v1.22"
+  beta: "v1.22"
+  stable: "TODO"