docs(opcua): fix stale NodeWriteRouter reference in EnsureVariable comment

src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/OtOpcUaNodeManager.cs

@@ -850,7 +850,7 @@ public sealed class OtOpcUaNodeManager : CustomNodeManager2
             };
             // Task 11: a writable equipment tag owns an inbound-write handler. The SDK invokes
             // OnWriteValue on a client write; it gates on the WriteOperate role and routes to the backing
-            // driver via NodeWriteRouter. Read-only nodes leave it null (the default) so a write is
+            // driver via NodeWriteGateway. Read-only nodes leave the handler unattached so a write is
             // rejected by the SDK's own AccessLevel check before it ever reaches a handler.
             if (writable)
             {