Removed duplicated include

Change-Id: I1b4cf0dcb18c1eeccb1155c4d4f1462050993aab
Reviewed-on: https://gerrit.libreoffice.org/53277Reviewed-by: Julien Nabet <serval2412@yahoo.fr>
Tested-by: Jenkins <ci@libreoffice.org>

vcl/source/gdi/bitmap4.cxx

@@ -28,7 +28,6 @@
 #include <vcl/BitmapSepiaFilter.hxx>
 #include <vcl/BitmapMosaicFilter.hxx>
 #include <vcl/BitmapEmbossGreyFilter.hxx>
-#include <vcl/BitmapSepiaFilter.hxx>
 #include <vcl/BitmapPopArtFilter.hxx>
 #include <vcl/BitmapDuoToneFilter.hxx>