build(aio): fix API docs breadcrumbs (angular#22446)

This also prevents some extra `<a>` elements inserted by the browser's
trying to fix the HTML structure, which also fixes the `.header-link`
added in ToC.

Fixes angular#22387
Closes angular#22437

PR Close angular#22446

Author: gkalpak

aio/tools/transforms/templates/api/base.template.html

@@ -22,7 +22,7 @@
       </script>
     {% for crumb in doc.breadCrumbs %}{% if not loop.last %}
       {$ slash() $}
-      {% if crumb.path %}<a href="{$ crumb.path $}">{$ crumb.text $}<a>{% else %}{$ crumb.text $}{% endif %}
+      {% if crumb.path %}<a href="{$ crumb.path $}">{$ crumb.text $}</a>{% else %}{$ crumb.text $}{% endif %}
     {% endif %}{% endfor %}
   </div>
   <header class="api-header">
@@ -43,4 +43,4 @@ <h1>
   <div class="api-body">
     {% block body %}{% endblock %}
   </div>
-</article>
+</article>