drop unneeded forward declare

Change-Id: I6a748d76bb24661404d280236f4c850a9136bb30
Reviewed-on: https://gerrit.libreoffice.org/70430
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

cui/source/factory/dlgfact.hxx

@@ -26,7 +26,6 @@
 #include <tools/link.hxx>
 #include <com/sun/star/frame/XFrame.hpp>
 
-class SfxTabDialog;
 class SfxModalDialog;
 class SfxSingleTabDialogController;
 class Dialog;