Since 1.21, Kubernetes clusters are enabled to support dual-stack networking by default.
In 1.23, the `IPv6DualStack` feature gate is removed.
The use of dual-stack networking is not mandatory.
Although clusters are enabled to support dual-stack networking, Pods and Services continue to default to single-stack.

The cause PR is [reverted](https://github.com/kubernetes/kubernetes/pull/117194) by v1.26.1.

## Urgent Upgrade Notes 

### (No, really, you MUST read this before you upgrade)

- 'The `IPv6DualStack` feature gate for external cloud providers was removed.
  (The feature became GA in 1.23 and the gate was removed for all other
  components several releases ago.) If you were still manually

- Feature gates that graduated to GA in 1.23 or earlier and were unconditionally enabled have been removed: CSIServiceAccountToken, ConfigurableFSGroupPolicy, EndpointSlice, EndpointSliceNodeName, EndpointSliceProxying, GenericEphemeralVolume, IPv6DualStack, IngressClassNamespacedParams, StorageObjectInUseProtection, TTLAfterFinished, VolumeSubpath, WindowsEndpointSliceProxying. ([#109435](https://github.com/kubernetes/kubernetes/pull/109435), [@pohly](https://github.com/pohly))

- Kubeadm: remove the `IPv6DualStack` feature gate. The feature has been GA and locked to enabled since 1.23. ([#106648](https://github.com/kubernetes/kubernetes/pull/106648), [@calvin0327](https://github.com/calvin0327))