Remove a duplicate OnColumnChange() call

If the width really changed, wxDataViewColumn::SetWidth() already calls
wxDataViewCtrl::OnColumnChange() (via UpdateWidth()), so it's
unnecessary to call the latter again immediately after calling the
former. And if the width didn't change, it's not necessary to call it at
all, so in either case the OnColumnChange() call can be just removed.

No real changes.

src/generic/datavgen.cpp

@@ -402,7 +402,6 @@ private:
 
         const unsigned col = event.GetColumn();
         owner->GetColumn(col)->SetWidth(event.GetWidth());
-        GetOwner()->OnColumnChange(col);
     }
 
     void OnEndReorder(wxHeaderCtrlEvent& event)