Removed unused include pngwrite in SlsBitmapFactory (sd)

Change-Id: I59305b415858ee1a826f03d9925624239cf7e582
Reviewed-on: https://gerrit.libreoffice.org/49291Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Julien Nabet <serval2412@yahoo.fr>

sd/source/ui/slidesorter/cache/SlsBitmapFactory.cxx

@@ -29,7 +29,6 @@
 #include <svx/svdpage.hxx>
 #include <vcl/bitmapex.hxx>
 #include <vcl/bitmapaccess.hxx>
-#include <vcl/pngwrite.hxx>
 
 namespace sd { namespace slidesorter { namespace view {
 class SlideSorterView;