Update index.html

Co-authored-by: Gregg Kellogg <[email protected]>

Author: pchampin

index.html

@@ -4257,7 +4257,7 @@ <h3>Algorithm</h3>
           the <span class="changed"><a data-lt="context-base-iri">base IRI</a> from <var>active context</var>, if it exists</span>.
           <span class="changed">To avoid confusion with a <a>keyword</a>, if <var>var</var> has the form of a keyword
           (i.e., it matches the ABNF rule `"@"1*ALPHA` from [[RFC5234]]),
-          prepend to it a colon followed by a a slash (`./`).</span>
+          prepend to it a period followed by a a slash (`./`).</span>
         </li>
         <li>Finally, return <var>var</var> as is.</li>
       </ol>