Docs: Improve JSDoc for for wp-admin/js/xfn.js.

Props kapteinbluf, igorsch.
Fixes #43204.

Built from https://develop.svn.wordpress.org/trunk@42715


git-svn-id: http://core.svn.wordpress.org/trunk@42543 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/js/xfn.js

@@ -1,3 +1,8 @@
+/**
+ * Generates the XHTML Friends Network 'rel' string from the inputs.
+ *
+ * @deprecated 3.5.0
+ */
 jQuery( document ).ready(function( $ ) {
 	$( '#link_rel' ).prop( 'readonly', true );
 	$( '#linkxfndiv input' ).bind( 'click keyup', function() {