qt: fix deprecation warning

```
../../modules/gui/qt/dialogs/preferences/simple_preferences.cpp: In constructor 'SPrefsPanel::SPrefsPanel(qt_intf_t*, QWidget*, int)':
WARNING : ../../modules/gui/qt/dialogs/preferences/simple_preferences.cpp:811: 52:  'void QButtonGroup::buttonClicked(int)' is deprecated: Use QButtonGroup::idClicked(int) instead [-Wdeprecated-declarations]
  811 |             connect( radioGroup, QOverload<int>::of(&QButtonGroup::buttonClicked),
      |                                  ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/x86_64-linux-gnu/qt5/QtWidgets/QButtonGroup:1,
                 from ../../modules/gui/qt/dialogs/preferences/simple_preferences.cpp:44:
/usr/include/x86_64-linux-gnu/qt5/QtWidgets/qbuttongroup.h:90:10: note: declared here
   90 |     void buttonClicked(int);
      |          ^~~~~~~~~~~~~
```