message: fix(issue-1622): remove TOC header text color
diff: @mixin themed-items {
  color: $text-01;
  background: $ui-background;
  - .#{$prefix}--tableofcontents__content {
  - h2,
  - h3,
  - h4 {
  - color: $text-01;
  - }
  - }
  .#{$prefix}--tableofcontents__mobile {
  border-top: 1px solid $ui-04;
  border-bottom: 1px solid $ui-04;
  