Fix Windows Hello bugs

* Fix #7977 - wrap key signing request in try/catch block to prevent crashes on some machines.
* Fix #8120 - try 3 times to bring Windows Hello prompt to front. This may be necessary on older machines that are slow to bring up the prompt window.

Also remove defunct code on macOS to prevent window focus issues.

src/gui/Application.cpp

@@ -209,12 +209,6 @@ bool Application::event(QEvent* event)
         emit openFile(static_cast<QFileOpenEvent*>(event)->file());
         return true;
     }
-#ifdef Q_OS_MACOS
-    // restore main window when clicking on the docker icon
-    else if (event->type() == QEvent::ApplicationActivate) {
-        emit applicationActivated();
-    }
-#endif
 
     return QApplication::event(event);
 }