### Preflight Checklist

- [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](https://www.github.com/electron/electron/issues) for a feature request that matches the one I want to file, without success.

### Electron Version

14.0.0

### What operating system are you using?

Ubuntu

### Operating System Version

Ubuntu 18.04

### What arch are you using?

x64

### Last Known Working Electron version

13.1.7

### Expected Behavior

The buttons in a (native) file dialog read "Cancel"  and "OK"

### Actual Behavior

The buttons in a native file dialog read `gtk-cancel` and `gtk-ok`.

### Testcase Gist URL

https://gist.github.com/Kilian/3de5f404d90d9b12ccaec817fdc4d6da

### Additional Information

Main window has a file input, click it to open the File chooser. Test on Ubuntu between 14.x and 13.x to see the difference. Probably caused by https://github.com/electron/electron/pull/19159

Electron 13.1.7:
![Selection_999(158)](https://user-images.githubusercontent.com/41970/126761063-a5361b8f-d057-406e-bb45-c71d48224b16.png)

Electron 14.0.0-beta.16
![Selection_999(156)](https://user-images.githubusercontent.com/41970/126761068-d6377aee-79f9-47a8-a3b5-f2a96578fda8.png)

shell/browser/ui/message_box_gtk.cc
public:
  explicit GtkMessageBox(const MessageBoxSettings& settings)
      : id_(settings.id),
        cancel_id_(settings.cancel_id),
        parent_(static_cast<NativeWindow*>(settings.parent_window)) {
    
    dialog_ =
        gtk_message_dialog_new(nullptr,                         
                               static_cast<GtkDialogFlags>(0),  
                               GetMessageType(settings.type),   
                               GTK_BUTTONS_NONE,                
                               "%s", settings.message.c_str());
    if (id_)
      GetDialogsMap()[*id_] = dialog_;
    if (!settings.detail.empty())
      gtk_message_dialog_format_secondary_text(GTK_MESSAGE_DIALOG(dialog_),
                                               "%s", settings.detail.c_str());
    if (!settings.title.empty())
      gtk_window_set_title(GTK_WINDOW(dialog_), settings.title.c_str());
    if (!settings.icon.isNull()) {
      
      
      static constexpr int pixel_width = 48;
      static constexpr int pixel_height = 48;
      GdkPixbuf* pixbuf =
          gtk_util::GdkPixbufFromSkBitmap(*settings.icon.bitmap());
      GdkPixbuf* scaled_pixbuf = gdk_pixbuf_scale_simple(