bench: add missing LaidOutWidget accessibility fields to lookup bench

benches/lookup.rs constructed LaidOutWidget without the accessible_label
and is_live_region fields added for accessibility, so cargo check
--all-targets failed to compile the bench. Set them to None / false.

benches/lookup.rs

@@ -43,6 +43,8 @@ fn build_widgets( n: usize ) -> Vec<LaidOutWidget<()>>
 			keyboard_focusable: true,
 			cursor:             ltk::CursorShape::Default,
 			tooltip:            None,
+			accessible_label:   None,
+			is_live_region:     false,
 		}
 	} ).collect()
 }