message: fix(ContentBlock): set inverse heading color
diff: @mixin content-block {
  .#{$prefix}--content-block--inverse {
  background-color: $inverse-02;
  +
  + .#{$prefix}--content-block__heading,
  + .#{$prefix}--content-block__copy p {
  color: $text-04;
  }
  + }
  .#{$prefix}--content-block {
  padding-top: $carbon--layout-03;
  padding-bottom: $carbon--layout-05;
  