Remove unnecessary trivial wxDisplayFactoryQt default ctor

No real changes, just remove useless lines.

src/qt/display.cpp

@@ -67,18 +67,11 @@ bool wxDisplayImplQt::ChangeMode(const wxVideoMode& WXUNUSED(mode))
 class wxDisplayFactoryQt : public wxDisplayFactory
 {
 public:
-    wxDisplayFactoryQt();
-
     virtual wxDisplayImpl *CreateDisplay(unsigned n) wxOVERRIDE;
     virtual unsigned GetCount() wxOVERRIDE;
     virtual int GetFromPoint(const wxPoint& pt) wxOVERRIDE;
 };
 
-    
-wxDisplayFactoryQt::wxDisplayFactoryQt()
-{
-}
-
 wxDisplayImpl *wxDisplayFactoryQt::CreateDisplay(unsigned n)
 {
     return new wxDisplayImplQt( n );