chore(network): reduce outdated connection prunning frequency

sn_networking/src/event/swarm.rs

@@ -605,6 +605,12 @@ impl SwarmDriver {
     // Remove outdated connection to a peer if it is not in the RT.
     // Optionally force remove all the connections for a provided peer.
     fn remove_outdated_connections(&mut self) {
+        // To avoid this being called too frequenctly, only carry out prunning intervally.
+        if Instant::now() > self.last_connection_pruning_time + Duration::from_secs(30) {
+            return;
+        }
+        self.last_connection_pruning_time = Instant::now();
+
         let mut removed_conns = 0;
         self.live_connected_peers.retain(|connection_id, (peer_id, timeout_time)| {