src: improve log messages

[joaoantoniocardoso]

Removes this:

2023-12-01T18:16:23.471247Z DEBUG ThreadId(68) src/stream/sink/webrtc_sink.rs:186: DTLS Transport: WebRTCDTLSTransport {
    inner: TypedObjectRef {
        inner: 0x00007fa400006970,
        type: GstWebRTCDTLSTransport,
    },
}

and improves this:

2023-12-01T18:16:45.489075Z DEBUG ThreadId(90) src/stream/sink/webrtc_sink.rs:380: Failed to send ICE candidate: Error {
    context: "Failed to send ICE candidate",
    source: SendError { .. },
}

and this:

2023-12-01T18:17:17.538817Z ERROR ThreadId(122) src/stream/sink/webrtc_sink.rs:477: Failed to send SDP offer: Failed to send SDP offer

Caused by:
    channel closed