Update index.html

Fix typo

Author: yezhizhen

index.html

@@ -3272,7 +3272,7 @@ <h3><dfn>Refresh</dfn></h3>
   </ol>
 
  <li><p><a>Set the current browsing context</a>
-  with <var>session</var> and <var>session</var>&apos;s<a>current
+  with <var>session</var> and <var>session</var>&apos;s <a>current
   top-level browsing context</a>.
 
  <li><p>Return <a>success</a> with data <a><code>null</code></a>.