edge: remove rtx from recv encoding parameters

Edge 14942 throws errors if that field is present.

Author: fippo

src/js/edge/edge_shim.js

@@ -362,6 +362,13 @@ var edgeShim = {
         transceiver.rtpSender.send(params);
       }
       if (recv && transceiver.rtpReceiver) {
+        // remove RTX field in Edge 14942
+        if (transceiver.kind === 'video'
+            && transceiver.recvEncodingParameters) {
+          transceiver.recvEncodingParameters.forEach(function(p) {
+            delete p.rtx;
+          });
+        }
         params.encodings = transceiver.recvEncodingParameters;
         params.rtcp = {
           cname: transceiver.cname