Remove __WXMSW__ check around background erasing in generic wxDataViewCtrl.

The background was erased only under MSW for some reason, do it everywhere
now.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72904 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/datavgen.cpp

@@ -1695,11 +1695,9 @@ void wxDataViewMainWindow::OnPaint( wxPaintEvent &WXUNUSED(event) )
     wxDataViewModel *model = GetModel();
     wxAutoBufferedPaintDC dc( this );
 
-#ifdef __WXMSW__
     dc.SetBrush(GetOwner()->GetBackgroundColour());
     dc.SetPen( *wxTRANSPARENT_PEN );
     dc.DrawRectangle(GetClientSize());
-#endif
 
     if ( IsEmpty() )
     {