update libp2p to 0.55 (#6889)

Updates libp2p to `0.55`.
Will address the deprecations in a subsequent PR

beacon_node/lighthouse_network/src/discovery/mod.rs

@@ -994,7 +994,7 @@ impl<E: EthSpec> NetworkBehaviour for Discovery<E> {
         &mut self,
         _peer_id: PeerId,
         _connection_id: ConnectionId,
-        _event: void::Void,
+        _event: std::convert::Infallible,
     ) {
     }
 

beacon_node/lighthouse_network/src/peer_manager/network_behaviour.rs

@@ -37,7 +37,10 @@ impl<E: EthSpec> NetworkBehaviour for PeerManager<E> {
         // no events from the dummy handler
     }
 
-    fn poll(&mut self, cx: &mut Context<'_>) -> Poll<ToSwarm<Self::ToSwarm, void::Void>> {
+    fn poll(
+        &mut self,
+        cx: &mut Context<'_>,
+    ) -> Poll<ToSwarm<Self::ToSwarm, std::convert::Infallible>> {
         // perform the heartbeat when necessary
         while self.heartbeat.poll_tick(cx).is_ready() {
             self.heartbeat();

beacon_node/lighthouse_network/src/rpc/handler.rs

@@ -353,6 +353,7 @@ where
         !matches!(self.state, HandlerState::Deactivated)
     }
 
+    #[allow(deprecated)]
     fn poll(
         &mut self,
         cx: &mut Context<'_>,
@@ -814,6 +815,7 @@ where
         Poll::Pending
     }
 
+    #[allow(deprecated)]
     fn on_connection_event(
         &mut self,
         event: ConnectionEvent<

beacon_node/lighthouse_network/src/service/mod.rs

@@ -1846,7 +1846,7 @@ impl<E: EthSpec> Network<E> {
                     None
                 }
                 #[allow(unreachable_patterns)]
-                BehaviourEvent::ConnectionLimits(le) => void::unreachable(le),
+                BehaviourEvent::ConnectionLimits(le) => libp2p::core::util::unreachable(le),
             },
             SwarmEvent::ConnectionEstablished { .. } => None,
             SwarmEvent::ConnectionClosed { .. } => None,