net/glib-networking: update to 2.76.0
- Drop -Denvironment_proxy=enabled in favor of default -Dlibproxy=enabled per https://gitlab.gnome.org/GNOME/glib-networking/-/commit/4cbc05cf75f2
Changes: https://gitlab.gnome.org/GNOME/glib-networking/-/blob/2.76.0/NEWS
PR: 270087
Requested by: tcberner