Remove SERVER_NAME var because of lighttpd bug

lighttpd suffers from the same same bug/feature apache does, it fills
SERVER_NAME in with the requested URL if connonical names and server
side server name is not configured.  No thanks.

Nginx seems to have secure defaults.

php/add.php

@@ -14,7 +14,6 @@ if(!isset($_POST['domain'], $_POST['list'], $_POST['token'])) {
 
 $SERVER_SIDE_IDS = [
     $_SERVER['SERVER_ADDR'],
-    $_SERVER['SERVER_NAME'],
     'pi.hole'
 ];