Bump webrtc and dtls library versions for Snowflake

It's been awhile since we bumped the version of webrtc and dtls.

The most recent release of https://github.com/pion/webrtc/ is v3.1.28. It includes the most recent version of https://github.com/pion/dtls/, which is v2.1.3. This includes the fingerprinting fixes we made to circumvent blocking in Russia (see #40014).

We should do a quick look at the other changes made and test it out to make sure everything works as we expect.