update comment of the method

[dodaydream]

The comments shows it sets an option of dompdf but it actually override the whole settings.

It seems is a wrapper function of this in dompdf

https://github.com/dompdf/dompdf/blob/643eb722100cfaff6c3e506e9a9b64add804256b/src/Dompdf.php#L1377

[dodaydream]

I created another pull request regarding on this, so i think its better to close it now.