remove crit! logging from ListenerClosed event on Ok() (#4821)

## Issue Addressed

Since adding Quic support on https://github.com/sigp/lighthouse/pull/4577, and due to `quinn`s api nature LH now triggers the [`ListenerClosed`](https://docs.rs/libp2p/0.52.3/libp2p/swarm/struct.ListenerClosed.html) event.. @michaelsproul noticed we are logging this event as `crit!` independently of the reason. This PR matches the reason, logging with `debug!` and `error!` (instead of `crit!`) according to its `Result`  
## Additional Info
LH will still log `crit!` until https://github.com/libp2p/rust-libp2p/pull/4621 has been merged

beacon_node/lighthouse_network/src/service/mod.rs

@@ -1602,7 +1602,14 @@ impl<AppReqId: ReqId, TSpec: EthSpec> Network<AppReqId, TSpec> {
                 SwarmEvent::ListenerClosed {
                     addresses, reason, ..
                 } => {
-                    crit!(self.log, "Listener closed"; "addresses" => ?addresses, "reason" => ?reason);
+                    match reason {
+                        Ok(_) => {
+                            debug!(self.log, "Listener gracefuly closed"; "addresses" => ?addresses)
+                        }
+                        Err(reason) => {
+                            crit!(self.log, "Listener abruptly closed"; "addresses" => ?addresses, "reason" => ?reason)
+                        }
+                    };
                     if Swarm::listeners(&self.swarm).count() == 0 {
                         Some(NetworkEvent::ZeroListeners)
                     } else {