untrackPeer method
Stops probing peerUId and forgets its offset. Call when the inlet goes
away — a stale offset for a departed peer is worse than none.
Implementation
void untrackPeer(String peerUId) {
for (final timer in _timers.remove(peerUId) ?? const <Timer>[]) {
timer.cancel();
}
_estimators.remove(peerUId);
offsets.remove(peerUId);
}