Modify title for the format vocabulaires, as there are now two

Author: Relequestual

jsonschema-validation.xml

@@ -509,7 +509,7 @@
             </section>
         </section>
 
-        <section title='A Vocabulary for Semantic Content With "format"' anchor="format">
+        <section title='Vocabularies for Semantic Content With "format"' anchor="format">
 
             <section title="Foreword">
                 <t>