message: Remove unused field in `scrollable::Scrollbar`
diff: @@ -199,7 +199,6 @@ impl<'a, Message, Renderer: crate::Renderer> Scrollable<'a, Message, Renderer> {
  Some(Scrollbar {
  outer_bounds,
  bounds: scrollbar_bounds,
  - margin: self.scrollbar_margin,
  scroller: Scroller {
  bounds: scroller_bounds,
  },
  @@ -720,9 +719,6 @@ struct Scrollbar {
  /// The bounds of the [`Scrollbar`].
  bounds: Rectangle,
  - /// The margin within the [`Scrollbar`].
  - margin: u16,
  -
  /// The bounds of the [`Scroller`].
  scroller: Scroller,
  }
  