### 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
const std::string lower = base::ToLowerASCII(text);
    if (lower == "cancel")
      return gtk_util::kCancelLabel;
    if (lower == "no")
      return gtk_util::kNoLabel;
    if (lower == "ok")
      return gtk_util::kOkLabel;
    if (lower == "yes")
      return gtk_util::kYesLabel;
    return text.c_str();
  }
  void Show() {
    gtk_widget_show(dialog_);
#if defined(USE_X11)
    if (!features::IsUsingOzonePlatform()) {
      
      
      x11::Time time = ui::X11EventSource::GetInstance()->GetTimestamp();
      gtk_window_present_with_time(GTK_WINDOW(dialog_),
                                   static_cast<uint32_t>(time));
    }
#endif
  }
  int RunSynchronous() {
    Show();
    int response = gtk_dialog_run(GTK_DIALOG(dialog_));
    return (response < 0) ? cancel_id_ : response;
  }
  void RunAsynchronous(MessageBoxCallback callback) {