Fix feature gate status for ContainerCheckpoint in v1.30

Author: tengqm

content/en/docs/reference/command-line-tools-reference/feature-gates/container-checkpoint.md

@@ -9,6 +9,10 @@ stages:
  - stage: alpha
  defaultValue: false
  fromVersion: "1.25"
+ toVersion: "1.29"
+ - stage: beta
+ defaultValue: true
+ fromVersion: "1.30"
 ---
 Enables the kubelet `checkpoint` API.
 See [Kubelet Checkpoint API](/docs/reference/node/kubelet-checkpoint-api/) for more details.

content/en/docs/reference/node/kubelet-checkpoint-api.md

@@ -4,8 +4,7 @@ title: Kubelet Checkpoint API
 weight: 10
 ---
 
-
-{{< feature-state for_k8s_version="v1.25" state="alpha" >}}
+{{< feature-state feature_gate_name="ContainerCheckpoint" >}}
 
 Checkpointing a container is the functionality to create a stateful copy of a
 running container. Once you have a stateful copy of a container, you could