minor code improvement on the affiliate's admin message

Line 530 of file affiliateincludes/classes/affiliateadmin.php reads this:

echo "<div class='message'style='width: 98%; margin-top: 20px; background-color: #FFFEEB; margin-left: auto; margin-right: auto; margin-bottom: 20px; border: 1px #e6db55 solid; padding: 10px;'>";

It would be better (and simpler) to do it like this:
echo "<div class='updated'>";
The end result is exactly the same, it's wordpress standard and easier to manipulate using administration themes!