Update spec/index.html

Co-authored-by: Ted Thibodeau Jr <[email protected]>

Author: afs

spec/index.html

@@ -1043,7 +1043,7 @@ <h4>RDF Reference IRIs</h4>
       </p>
       <p>
         An <dfn data-lt="RDF reference">RDF Reference IRI</dfn>,
-        sometimes just called <a>RDF Reference</a>,
+        sometimes called simply <a>RDF Reference</a>,
         is an <a>IRI</a> that is suitable for use as a global reference.
       </p>