webrtc.ConfigureNack() only wires up the NACK RTCP interceptor. pion
still needs an explicit RTX codec registered per media codec before it
can answer a publisher's retransmission offer with one, so
incomingVideoCodecs having none means NACK-triggered retransmission
can never actually happen for incoming video, no matter what the
publisher offers.
Fixes#5678
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Co-authored-by: aler9 <46489434+aler9@users.noreply.github.com>