gluon-core: remove obsolete dnsmasq upgrade script

The script cleaned up an old setting that was removed in 2014.

package/gluon-core/files/lib/gluon/upgrade/100-dnsmasq

-#!/bin/sh
-
-if [ -e /etc/dnsmasq.conf ]; then
-	sed -i -e '/^conf-dir=\/lib\/gluon\/dnsmasq\.d$/d' -e '/^conf-dir=\/var\/gluon\/dnsmasq\.d$/d' /etc/dnsmasq.conf
-fi