bootstrap-tokens: promote to GA in 1.18 (#18428)

content/en/docs/reference/access-authn-authz/authentication.md

@@ -120,7 +120,7 @@ Authorization: Bearer 31ada4fd-adec-460c-809a-9e56ceb75269
 
 ### Bootstrap Tokens
 
-This feature is currently in **beta**.
+{{< feature-state for_k8s_version="v1.18" state="stable" >}}
 
 To allow for streamlined bootstrapping for new clusters, Kubernetes includes a
 dynamically-managed Bearer token type called a *Bootstrap Token*. These tokens

content/en/docs/reference/access-authn-authz/bootstrap-tokens.md

@@ -7,6 +7,9 @@ weight: 20
 ---
 
 {{% capture overview %}}
+
+{{< feature-state for_k8s_version="v1.18" state="stable" >}}
+
 Bootstrap tokens are a simple bearer token that is meant to be used when
 creating new clusters or joining new nodes to an existing cluster.  It was built
 to support [kubeadm](/docs/reference/setup-tools/kubeadm/kubeadm/), but can be used in other contexts
@@ -26,8 +29,6 @@ Controller Manager.  The tokens are also used to create a signature for a
 specific ConfigMap used in a "discovery" process through a BootstrapSigner
 controller.
 
-{{< feature-state state="beta" >}}
-
 ## Token Format
 
 Bootstrap Tokens take the form of `abcdef.0123456789abcdef`.  More formally,

content/en/docs/reference/command-line-tools-reference/kubelet-tls-bootstrapping.md

@@ -117,7 +117,7 @@ While any authentication strategy can be used for the kubelet's initial
 bootstrap credentials, the following two authenticators are recommended for ease
 of provisioning.
 
-1. [Bootstrap Tokens](#bootstrap-tokens) - __beta__
+1. [Bootstrap Tokens](#bootstrap-tokens)
 2. [Token authentication file](#token-authentication-file)
 
 Bootstrap tokens are a simpler and more easily managed method to authenticate kubelets, and do not require any additional flags when starting kube-apiserver.