negotiate-timing: fix concealedSamples measurement

which was still looking for the removed track stats

Author: fippo

src/content/peerconnection/negotiate-timing/js/main.js

@@ -199,7 +199,7 @@ async function getAudioImpairment(audioTransceiver) {
   const stats = await audioTransceiver.receiver.getStats();
   let currentImpairment;
   stats.forEach(stat => {
-    if (stat.type == 'track') {
+    if (stat.type == 'inbound-rtp') {
       currentImpairment = stat.concealedSamples;
     }
   });