doc: fix c++ addon hello world sample

PR-URL: #56172
Refs: #56173
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>
Reviewed-By: theanarkh <theratliter@gmail.com>

doc/api/addons.md

@@ -72,14 +72,15 @@ namespace demo {
 using v8::FunctionCallbackInfo;
 using v8::Isolate;
 using v8::Local;
+using v8::NewStringType;
 using v8::Object;
 using v8::String;
 using v8::Value;
 
 void Method(const FunctionCallbackInfo<Value>& args) {
   Isolate* isolate = args.GetIsolate();
   args.GetReturnValue().Set(String::NewFromUtf8(
-      isolate, "world").ToLocalChecked());
+      isolate, "world", NewStringType::kNormal).ToLocalChecked());
 }
 
 void Initialize(Local<Object> exports) {