### 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
callback_ = std::move(callback);
    g_signal_connect(dialog_, "delete-event",
                     G_CALLBACK(gtk_widget_hide_on_delete), nullptr);
    g_signal_connect(dialog_, "response", G_CALLBACK(OnResponseDialogThunk),
                     this);
    Show();
  }
  void OnWindowClosed() override {
    parent_->RemoveObserver(this);
    parent_ = nullptr;
  }
  CHROMEG_CALLBACK_1(GtkMessageBox, void, OnResponseDialog, GtkWidget*, int);
  CHROMEG_CALLBACK_0(GtkMessageBox, void, OnCheckboxToggled, GtkWidget*);
 private:
  electron::UnresponsiveSuppressor unresponsive_suppressor_;
  
  absl::optional<int> id_;
  
  int cancel_id_ = 0;
  bool checkbox_checked_ = false;
  NativeWindow* parent_;
  GtkWidget* dialog_;
  MessageBoxCallback callback_;
  DISALLOW_COPY_AND_ASSIGN(GtkMessageBox);
};
void GtkMessageBox::OnResponseDialog(GtkWidget* widget, int response) {