kubeadm: move the RootlessControlPlane FG to deprecated

[neolit123]

The feature was left in alpha for a few releases, since k8s started planning on a broader feature UserNamespacesSupport, which is what kubeadm should integrate with.

UserNamespacesSupport graduated to beta in 1.30.
Once it graduates to GA kubeadm can start using it an remove RootlessControlPlane.

/sig cluster-lifecycle

kubernetes/kubeadm#2473 (comment)
kubernetes/kubernetes#124997

[neolit123]

/cc @SataQiu @pacoxu

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[neolit123]

/kind deprecation

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[neolit123]

kubernetes/kubernetes#124997 merged
PTAL for LGTM
@pacoxu @SataQiu

[SataQiu]

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 34f13ef79970da18fcf3de2280d1b5ea6fd91a1c

[pacoxu]

/lgtm
/assign @tengqm

[tengqm]

/approve

[k8s-ci-robot]

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