style(peer): format security hardening

Record the deterministic nightly rustfmt output for the newly added event-channel and retry code after the repository-wide formatter gate was repaired.

Test Plan:
- just fmt
- just clippy
- git diff --check

crates/lanspread-peer/src/services/liveness.rs

@@ -3,6 +3,7 @@
 use std::{sync::Arc, time::Duration};
 
 use futures::{StreamExt as _, stream};
+
 use crate::{
     PeerEventSender,
     config::{PEER_PING_IDLE_SECS, PEER_PING_INTERVAL_SECS, peer_stale_timeout},