message: Remove `Default` constraint for checkbox `Color`
diff: @@ -191,7 +191,7 @@ pub trait Renderer {
  impl<'a, Color, Message, Renderer> From<Checkbox<Color, Message>>
  for Element<'a, Message, Renderer>
  where
  - Color: 'static + Copy + Default + std::fmt::Debug,
  + Color: 'static + Copy + std::fmt::Debug,
  Renderer: self::Renderer + text::Renderer<Color>,
  Message: 'static,
  {
  