build(docs-infra): improve @usageNotes message (#42888)

improve the @usageNotes message by adding the word "is"
(outcome: "Further information is available in...", compared to
"Further information available in...")

PR Close #42888

aio/tools/transforms/templates/api/includes/description.html

@@ -2,7 +2,7 @@
 <section class="description">
   <h2>Description</h2>
   {$ doc.description | trimBlankLines | marked $}
-  {% if doc.usageNotes %}<p>Further information available in the <a href="#usage-notes">Usage Notes...</a></p>{%
+  {% if doc.usageNotes %}<p>Further information is available in the <a href="#usage-notes">Usage Notes...</a></p>{%
   endif %}
 </section>
 {% endif %}