Want Remove Pragma:no-cache in HTTP Header

hi all, i have working with opencart 1.5.6 and we have site and its working fine. now we are doing seo process. the seo team ask us to remove

"Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0" and "Pragma: no-cache".

i have unset above two in htaccess and add cache header in opencart's config.php. but when we check its always return the same.

here i have attached the screenshot of http response. please help me soon..