www/epiphany: remove unnecessary dependency on net/avahi-app

Upstream of the epiphany removed dependency from avahi in 2016, check NEWS file
(/usr/ports/www/epiphany/work/epiphany-3.28.5/NEWS):

3.23.1 - October 24, 2016

Epiphany has been relicensed from GPLv2+ to GPLv3+.

New dependency:
libhttpseverywhere
Removed dependencies:
avahi-client, avahi-gobject, gdk-x11-3.0, gsettings-desktop-schemas, x11

PR: 247378
Submitted by: VVD <vvd@unislabs.com>
Approved by: gnome (timeout)