message: Eliminate some extraneous button margin in Boxel::InputGroup
diff: border: 1px solid var(--boxel-input-group-border-color);
  border-radius: var(--boxel-input-group-border-radius);
  transition: border-color var(--boxel-transition);
  + margin: 0;
  min-height: var(--boxel-input-group-height);
  outline-offset: 0;
  }
  .boxel-input-group__text-accessory {
  - display: flex;
  align-items: center;
  - padding: var(--boxel-input-group-padding-y) var(--boxel-input-group-padding-x);
  + background-color: var(--boxel-light-400);
  + color: var(--boxel-purple-900);
  + display: flex;
  font-size: var(--boxel-font-size-sm);
  line-height: var(--boxel-ratio);
  - color: var(--boxel-purple-900);
  + padding: var(--boxel-input-group-padding-y) var(--boxel-input-group-padding-x);
  text-align: center;
  white-space: nowrap;
  - background-color: var(--boxel-light-400);
  }
  .boxel-input-group__button-accessory,
  