rtc.advertise_internal_ip (which lets LAN callers reach the SFU via a LAN
host candidate, avoiding NAT-hairpin on the router) is only honoured when
node_ip is set manually from LiveKit v1.13.6 (mediatransportutil f234b53).
nixpkgs-unstable currently ships 1.13.5, so pin 1.13.6 with the hashes from
nixpkgs master. Remove this override once nixpkgs-unstable reaches >= 1.13.6.
