Remove HTTP not working on specific headers

Problem/Motivation

I try to remove Server and X-Powered-By to suppress server and PHP informations for my website security.

Steps to reproduce

Add this lines if the configuration form :

Server
X-Powered-By
X-Generator

Proposed resolution

Only X-Generator is deleted. I don't know if it's possible to delete Server and X-Powered-By with the module but it could be really useful to be able to.