kubeadm: update feature gates and add removed FGs (#42771)

* kubeadm: remove UnversionedKubeletConfigMap

* kuebadm: add IPv6DualStack to removed FG

* kubeadm: add EtcdLearnerMode FG descriptions

content/en/docs/reference/setup-tools/kubeadm/kubeadm-init.md

@@ -159,7 +159,7 @@ Feature | Default | Alpha | Beta | GA
 :-------|:--------|:------|:-----|:----
 `PublicKeysECDSA` | `false` | 1.19 | - | -
 `RootlessControlPlane` | `false` | 1.22 | - | -
-`UnversionedKubeletConfigMap` | `true` | 1.22 | 1.23 | 1.25
+`EtcdLearnerMode` | `false` | 1.27 | - | -
 {{< /table >}}
 
 {{< note >}}
@@ -179,15 +179,9 @@ for `kube-apiserver`, `kube-controller-manager`, `kube-scheduler` and `etcd` to
 If the flag is not set, those components run as root. You can change the value of this feature gate before
 you upgrade to a newer version of Kubernetes.
 
-`UnversionedKubeletConfigMap`
+`EtcdLearnerMode`
-: This flag controls the name of the {{< glossary_tooltip text="ConfigMap" term_id="configmap" >}} where kubeadm stores
+: With this feature gate enabled, when joining a new control plane node, a new etcd member will be created
-kubelet configuration data. With this flag not specified or set to `true`, the ConfigMap is named `kubelet-config`.
+as a learner and promoted to a voting member only after the etcd data are fully aligned.
-If you set this flag to `false`, the name of the ConfigMap includes the major and minor version for Kubernetes
-(for example: `kubelet-config-{{< skew currentVersion >}}`). Kubeadm ensures that RBAC rules for reading and writing
-that ConfigMap are appropriate for the value you set. When kubeadm writes this ConfigMap (during `kubeadm init`
-or `kubeadm upgrade apply`), kubeadm respects the value of `UnversionedKubeletConfigMap`. When reading that ConfigMap
-(during `kubeadm join`, `kubeadm reset`, `kubeadm upgrade ...`), kubeadm attempts to use unversioned ConfigMap name first;
-if that does not succeed, kubeadm falls back to using the legacy (versioned) name for that ConfigMap.
 
 List of deprecated feature gates:
 
@@ -213,6 +207,31 @@ instance is upgraded. The deprecated `UpgradeAddonsBeforeControlPlane` feature g
 behavior. You should not need this old behavior; if you do, you should consider changing your cluster or upgrade processes, as this
 feature gate will be removed in a future release.
 
+List of removed feature gates:
+
+{{< table caption="kubeadm removed feature gates" >}}
+Feature | Alpha | Beta | GA | Removed
+:-------|:------|:-----|:---|:-------
+`UnversionedKubeletConfigMap` | 1.22 | 1.23 | 1.25 | 1.26
+`IPv6DualStack` | 1.16 | 1.21 | 1.23 | 1.24
+{{< /table >}}
+
+Feature gate descriptions:
+
+`UnversionedKubeletConfigMap`
+: This flag controls the name of the {{< glossary_tooltip text="ConfigMap" term_id="configmap" >}} where kubeadm stores
+kubelet configuration data. With this flag not specified or set to `true`, the ConfigMap is named `kubelet-config`.
+If you set this flag to `false`, the name of the ConfigMap includes the major and minor version for Kubernetes
+(for example: `kubelet-config-{{< skew currentVersion >}}`). Kubeadm ensures that RBAC rules for reading and writing
+that ConfigMap are appropriate for the value you set. When kubeadm writes this ConfigMap (during `kubeadm init`
+or `kubeadm upgrade apply`), kubeadm respects the value of `UnversionedKubeletConfigMap`. When reading that ConfigMap
+(during `kubeadm join`, `kubeadm reset`, `kubeadm upgrade ...`), kubeadm attempts to use unversioned ConfigMap name first;
+if that does not succeed, kubeadm falls back to using the legacy (versioned) name for that ConfigMap.
+
+`IPv6DualStack`
+: This flag helps to configure components dual stack when the feature is in progress. For more details on Kubernetes
+dual-stack support see [Dual-stack support with kubeadm](/docs/setup/production-environment/tools/kubeadm/dual-stack-support/).
+
 ### Adding kube-proxy parameters {#kube-proxy}
 
 For information about kube-proxy parameters in the kubeadm configuration see: