h() function is Convenience wrapper for htmlspecialchars() in cakephp. It Convert special characters to HTML entities. So you are getting the warning.
Syntax for this function is h(string $text, boolean $double = true, string $charset = null)
To style your code you can use this alternatively
<?php
echo $this->Html->tag('span', $product['Product']['name'], array('style' => 'font-weight:bold;'));
?>
// Output
<span style="font-weight:bold;">Your Product Name</span>