promote DisableNodeKubeProxyVersion feature gate to beta

Author: HirazawaUi

content/en/docs/reference/command-line-tools-reference/feature-gates/disable-node-kube-proxy-version.md

@@ -9,5 +9,9 @@ stages:
   - stage: alpha
     defaultValue: false
     fromVersion: "1.29"
+    toVersion: "1.30"
+  - stage: beta
+    defaultValue: true
+    fromVersion: "1.31"
 ---
 Disable setting the `kubeProxyVersion` field of the Node.