Update pion-webrtc version to 2.2.3

We recently tracked down some issues with the pion library that were causing inefficiencies and infinite loops to occur (see legacy/trac#33211 (moved)).

These have been addressed in pion-dtls v2.0.0-rc.7 and pion-sctp v1.7.5. I'd suggest just bumping to the latest version of pion-webrtc v2.2.3, which includes version bumps for each of these supporting libraries.