KEP-3836 - v1.31 doc update

Author: alexanderConstantinescu

content/en/docs/reference/command-line-tools-reference/feature-gates/kube-proxy-draining-terminating-nodes.md

@@ -13,6 +13,10 @@ stages:
   - stage: beta
     defaultValue: true
     fromVersion: "1.30"
+    toVersion: "1.31"
+  - stage: stable
+    defaultValue: true
+    fromVersion: "1.31"
 ---
 Implement connection draining for
 terminating nodes for `externalTrafficPolicy: Cluster` services.