added link for Fibers.

Should we move class.fibers page to language.fibers?

Author: mumumu

appendices/migration81/new-features.xml

@@ -72,7 +72,7 @@
    <title>Fibers</title>
 
    <para>
-    Support for <!--<link linkend="language.fibers">-->Fibers<!--</link>--> has been added.
+    Support for <link linkend="class.fiber">Fibers</link> has been added.
     <!-- RFC: https://wiki.php.net/rfc/fibers -->
    </para>
   </sect3>