message: fix(leadspace-centered): use color token for gradient
diff: &__gradient {
  background: linear-gradient(
  to bottom,
  - rgba(0, 0, 0, 0.8),
  - rgba(0, 0, 0, 0.6),
  + rgba($ui-background, 0.8),
  + rgba($ui-background, 0.6),
  transparent 75%
  );
  }
  