message: docs(aio): fix missing anchor-open in i18n documentation
  The Internationalisation documentation, "Translate text nodes" section, has an incomplete
  markdown anchor, and leaks markdown into the page. Fix the anchor by adding the opening bracket.
diff: @@ -408,7 +408,7 @@ This XML element represents the translation of the `<h1>` greeting tag you marke
  <div class="l-sub-section">
  -Note that the translation unit `id=introductionHeader` is derived from the _custom_ `id`](#custom-id "Set a custom id") that you set earlier, but **without the `@@` prefix** required in the source HTML.
  +Note that the translation unit `id=introductionHeader` is derived from the [_custom_ `id`](#custom-id "Set a custom id") that you set earlier, but **without the `@@` prefix** required in the source HTML.
  </div>
  