vcl: remove duplicate forward

Change-Id: Id6021cae4bbde8e420ee82e311f4221e49199ef9
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/103716
Tested-by: Jenkins
Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>
diff --git a/include/vcl/layout.hxx b/include/vcl/layout.hxx
index 3a5adbc..519d9bf 100644
--- a/include/vcl/layout.hxx
+++ b/include/vcl/layout.hxx
@@ -25,7 +25,6 @@
#include <set>

class ScrollBar;
class ScrollBar;
class ScrollBarBox;
class Splitter;