docs: remove uneeded 2nd param in sample code

Author: kenjis

user_guide_src/source/helpers/text_helper/009.php

@@ -1,4 +1,4 @@
 <?php
 
 $string = 'Fred, Bill,, Joe, Jimmy';
-$string = reduce_multiples($string, ','); // results in "Fred, Bill, Joe, Jimmy"
+$string = reduce_multiples($string); // results in "Fred, Bill, Joe, Jimmy"