Include reception reoprts in receiver report callback. (#4496)

Media loss proxy is not use, so it is okay, but was an unintentional
delete in https://github.com/livekit/livekit/pull/3252/changes

Was checking code due to a report of how Chrome does RTCP reports in
147+ breaking a few services. Don't think that affects LK, but found
this while reading code.

pkg/sfu/downtrack.go

@@ -2018,6 +2018,7 @@ func (d *DownTrack) handleRTCP(bytes []byte) {
 				if r.SSRC != d.ssrc {
 					continue
 				}
+				rr.Reports = append(rr.Reports, r)
 
 				rtt, isRttChanged := d.rtpStats.UpdateFromReceiverReport(r)
 				if isRttChanged {