Reduce outgoing peers demand (#2969)

* reduce demand

* use `saturating_sub`

zebra-network/src/peer_set/initialize.rs

@@ -199,8 +199,12 @@ where
     );
     let _ = candidates.update_initial(active_initial_peer_count).await;
 
-    // TODO: reduce demand by `active_outbound_connections.update_count()` (#2902)
-    for _ in 0..config.peerset_initial_target_size {
+    // Compute remaining connections to open.
+    let demand_count = config
+        .peerset_initial_target_size
+        .saturating_sub(active_outbound_connections.update_count());
+
+    for _ in 0..demand_count {
         let _ = demand_tx.try_send(MorePeers);
     }