Update description about node Lease feature.

content/en/docs/concepts/architecture/nodes.md

@@ -174,9 +174,8 @@ ConditionUnknown and 5m after that to start evicting pods.) The node controller
 checks the state of each node every `--node-monitor-period` seconds.
 
 In versions of Kubernetes prior to 1.13, NodeStatus is the heartbeat from the
-node. Starting from Kubernetes 1.13, node lease feature is introduced as an
-alpha feature (feature gate `NodeLease`,
-[KEP-0009](https://github.com/kubernetes/enhancements/blob/master/keps/sig-node/0009-node-heartbeat.md)).
+node. Node lease feature is enabled by default since 1.14 as a beta feature
+(feature gate `NodeLease`, [KEP-0009](https://github.com/kubernetes/enhancements/blob/master/keps/sig-node/0009-node-heartbeat.md)).
 When node lease feature is enabled, each node has an associated `Lease` object in
 `kube-node-lease` namespace that is renewed by the node periodically, and both
 NodeStatus and node lease are treated as heartbeats from the node. Node leases