doc: hello addon example should return "world"

The N-API version of the hello example, returned "hello" instead of "world".

doc/api/addons.md

@@ -408,7 +408,7 @@ napi_value Method(napi_env env, napi_callback_info args) {
  napi_value greeting;
  napi_status status;
 
- status = napi_create_string_utf8(env, "hello", NAPI_AUTO_LENGTH, &greeting);
+ status = napi_create_string_utf8(env, "world", NAPI_AUTO_LENGTH, &greeting);
  if (status != napi_ok) return nullptr;
  return greeting;
 }