[GUI] Remove code for Qt < 5.9

src/Gui/Action.cpp

@@ -37,9 +37,7 @@
 # include <QToolButton>
 #endif
 
-#if QT_VERSION >= QT_VERSION_CHECK(5, 0, 0)
-# include <QScreen>
-#endif
+#include <QScreen>
 
 #include <Base/Tools.h>
 #include "Action.h"
@@ -431,11 +429,7 @@ void WorkbenchComboBox::showPopup()
     int rows = count();
     if (rows > 0) {
         int height = view()->sizeHintForRow(0);
-#if QT_VERSION >= QT_VERSION_CHECK(5, 0, 0)
         int maxHeight = QApplication::primaryScreen()->size().height();
-#else
-        int maxHeight = QApplication::desktop()->height();
-#endif
         view()->setMinimumHeight(qMin(height * rows, maxHeight/2));
     }