message: fix(expressive): icon only button expressive styling
diff: /// @access private
  /// @group button-expressive
  @mixin button-expressive {
  - .#{$prefix}--btn--sm {
  - min-height: rem(40px);
  - }
  -
  - .#{$prefix}--btn {
  - &__icon {
  + .#{$prefix}--btn .#{$prefix}--btn__icon {
  width: auto;
  height: auto;
  }
  +
  + .#{$prefix}--btn--icon-only {
  + padding: calc(0.875rem - 3px);
  +
  + &.#{$prefix}--btn--tertiary {
  + padding: calc(0.875rem - 1px);
  + }
  +
  + &.#{$prefix}--btn--field,
  + &.#{$prefix}--btn--sm {
  + padding: rem(7px);
  + }
  +
  + &.#{$prefix}--btn--field.#{$prefix}--btn--tertiary,
  + &.#{$prefix}--btn--sm.#{$prefix}--btn--tertiary {
  + padding: rem(9px);
  + }
  }
  }
  