Update spec/index.html

Co-authored-by: Thomas Tanon <[email protected]>

Author: afs

spec/index.html

@@ -6721,7 +6721,7 @@ <h4>Functions on Strings</h4>
             <li>a literal with datatype <code>xsd:string</code></li>
             <li>a literal with datatype <code>rdf:langString</code> and
               with <a data-cite="RDF12-CONCEPTS#dfn-language-tag">language tag</a></li>
-            <li>a literal with datatype <code>rdf:langString</code> and 
+            <li>a literal with datatype <code>rdf:dirLangString</code> and 
               with both a <a data-cite="RDF12-CONCEPTS#dfn-language-tag">language tag</a>
               and a <a data-cite="RDF12-CONCEPTS#dfn-base-direction">base direction</a></li>
           </ul>