Backport of "rtpopusdepay: missing sprop-stereo should not assume mono" into 1.20
requested to merge tpm/gstreamer:backport-mr-2125-into-1.20-bugfix-no-force-mono-missing-sprop into 1.20
Backport of !2125 (merged) "rtpopusdepay: missing sprop-stereo should not assume mono".
Commits:
- 86f0f8b6 rtpopusdepay: assume 2 channels if sprop-stereo is missing