drop unused cuilo-BackgroundPreview from catalog

Change-Id: Ib8707b29c44291fe18d86660d9bfaaed742afbd6
Reviewed-on: https://gerrit.libreoffice.org/60716
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

extras/source/glade/libreoffice-catalog.xml.in

@@ -218,9 +218,6 @@
     <glade-widget-class title="Document Preview Window" name="sdlo-SdDocPreviewWin"
                         generic-name="Document Preview Window" parent="GtkDrawingArea"
                         icon-name="widget-gtk-drawingarea"/>
-    <glade-widget-class title="Background Preview" name="cuilo-BackgroundPreview"
-                        generic-name="Background Preview Window" parent="GtkDrawingArea"
-                        icon-name="widget-gtk-drawingarea"/>
     <glade-widget-class title="Rectangle Preview" name="svxlo-SvxXRectPreview"
                         generic-name="Rectangle Preview Window" parent="GtkDrawingArea"
                         icon-name="widget-gtk-drawingarea"/>