webrtc: strip TWCC extension of incoming RTP packets (#5146)

[aler9]

Fixes #5146

The TWCC extension is used as part of the WebRTC congestion control algorithm placed between the publisher and the server. If this extension is routed untouched from the server to readers, it messes with the congestion control algorithm present between the server and each reader. Remove it.

[codecov]

Codecov Report

❌ Patch coverage is 81.25000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.06%. Comparing base (33f1281) to head (471b132).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/protocols/webrtc/incoming_track.go	81.25%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5605      +/-   ##
==========================================
+ Coverage   62.02%   62.06%   +0.04%     
==========================================
  Files         205      205              
  Lines       17363    17379      +16     
==========================================
+ Hits        10769    10786      +17     
+ Misses       5709     5707       -2     
- Partials      885      886       +1     

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