message: [Improvement] Field: update clear icon color
diff: &__clear,
  &__icon {
  padding: 0 10px;
  - color: $gray-dark;
  line-height: inherit;
  margin-right: -10px;
  }
  + &__clear {
  + color: $gray;
  + }
  +
  &__icon .van-icon {
  display: block;
  font-size: 16px;
  + color: $gray-dark;
  line-height: inherit;
  }
  