[GUI] Remove code for Qt < 5.9

src/Gui/PropertyPage.cpp

@@ -116,9 +116,7 @@ PreferenceUiForm::PreferenceUiForm(const QString& fn, QWidget* parent)
   : PreferencePage(parent), form(0)
 {
     UiLoader loader;
-#if QT_VERSION >= 0x040500
     loader.setLanguageChangeEnabled(true);
-#endif
     loader.setWorkingDirectory(QFileInfo(fn).absolutePath());
     QFile file(fn);
     if (file.open(QFile::ReadOnly))