This remove use of MaybeWorkerThread* rtp_transport_queue_ from
AudioSendStream. The worker queue is alwauys assumed ot be used where
rtp_transport_queue_ was used.
Bug: webrtc:14502
Change-Id: Ia516ce7340d712671e0ecb301bba9d66e7216973
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/300400
Reviewed-by: Evan Shrubsole <eshr@webrtc.org>
Reviewed-by: Jakob Ivarsson <jakobi@webrtc.org>
Commit-Queue: Per Kjellander <perkj@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#39816}