### Preflight Checklist
<!-- Please ensure you've completed the following steps by replacing [ ] with [x]-->

* [x] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/master/CONTRIBUTING.md) for this project.
* [x] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project adheres to.
* [x] I have searched the issue tracker for an issue that matches the one I want to file, without success.

### Issue Details

* **Electron Version:**
  * 8.0.0
* **Operating System:**
  * Windows 10 Pro (1709)

### Expected Behavior
Using Notification API in main process with `timeoutType: 'never` I expected that the notification disappears only when the user clicks on it.  

### Actual Behavior
After few seconds the notification disappers.

### To Reproduce

```
  const newNotification = new Notification({title: 'I am a main process Notification!', timeoutType: 'never'})
  newNotification.show()
```

```sh
$ git clone https://github.com/p-fusi/electron-quick-start -b master
$ npm install
$ npm run start
```


shell/browser/notifications/win/windows_toast_notification.cc
ScopedHString tag(L"toast");
  if (!tag.success())
    return E_FAIL;
  ComPtr<IXmlNodeList> node_list;
  RETURN_IF_FAILED(doc->GetElementsByTagName(tag, &node_list));
  ComPtr<IXmlNode> root;
  RETURN_IF_FAILED(node_list->Item(0, &root));
  ComPtr<IXmlElement> audio_element;
  ScopedHString audio_str(L"audio");
  RETURN_IF_FAILED(doc->CreateElement(audio_str, &audio_element));
  ComPtr<IXmlNode> audio_node_tmp;
  RETURN_IF_FAILED(audio_element.As(&audio_node_tmp));
  
  ComPtr<IXmlNode> audio_node;
  RETURN_IF_FAILED(root->AppendChild(audio_node_tmp.Get(), &audio_node));
  
  ComPtr<IXmlNamedNodeMap> attributes;
  RETURN_IF_FAILED(audio_node->get_Attributes(&attributes));
  ComPtr<IXmlAttribute> silent_attribute;
  ScopedHString silent_str(L"silent");
  RETURN_IF_FAILED(doc->CreateAttribute(silent_str, &silent_attribute));
  ComPtr<IXmlNode> silent_attribute_node;
  RETURN_IF_FAILED(silent_attribute.As(&silent_attribute_node));
  
  ScopedHString silent_value(L"true");
  if (!silent_value.success())
    return E_FAIL;
  ComPtr<IXmlText> silent_text;
  RETURN_IF_FAILED(doc->CreateTextNode(silent_value, &silent_text));
  ComPtr<IXmlNode> silent_node;