If you can access functions.php file, use this code to de-register the schema manually:

add_action('wp_head', function() {
ob_start(function($buffer) {
return preg_replace('/<script[^>]+type=["\']rocketlazyloadscript["\'][^>]*>.*?<\/script>/is', '', $buffer);
});
}, 1);

This code filters out any <script type="rocketlazyloadscript"> </script> block from the page output but use only if you're sure it's safe to remove and you’ve isolated the right script.