audio: use Opus PLC and FEC

Audio glitches are noticed in case of packet drop. Use Opus PLC and FEC to improve audio quality

changed milestone to %Iteration 26

added enhancement label

added SprintIn progress label

added SprintTo review label and removed SprintIn progress label

changed milestone to %Iteration 27

closed

removed SprintTo review label

changed due date to April 01, 2021