webrtc: fix error "Failed to setup RTCP mux" on some readers (#3381)

[aler9]

Fixes #3381

[codecov]

Codecov Report

Attention: Patch coverage is 77.77778% with 6 lines in your changes missing coverage. Please review.

Project coverage is 56.23%. Comparing base (1911294) to head (aa339fc).
Report is 1 commits behind head on main.

Files	Patch %	Lines
internal/protocols/webrtc/peer_connection.go	77.77%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3449      +/-   ##
==========================================
+ Coverage   56.20%   56.23%   +0.02%     
==========================================
  Files         190      190              
  Lines       19049    19076      +27     
==========================================
+ Hits        10707    10727      +20     
- Misses       7520     7525       +5     
- Partials      822      824       +2     

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[github-actions]

This issue is mentioned in release v1.8.3 🚀
Check out the entire changelog by clicking here