Attempt to fix flaky basic sim test (#6134)

* Fix `target_peer` config for basic_sim, so a node doesn't disconnected by peers because of `TooManyPeers`.

testing/simulator/src/basic_sim.rs

@@ -37,6 +37,8 @@ pub fn run_basic_sim(matches: &ArgMatches) -> Result<(), String> {
         .unwrap_or(&String::from("0"))
         .parse::<usize>()
         .unwrap_or(0);
+    // extra beacon node added with delay
+    let extra_nodes: usize = 1;
     println!("PROPOSER-NODES: {}", proposer_nodes);
     let validators_per_node = matches
         .get_one::<String>("validators-per-node")
@@ -133,6 +135,7 @@ pub fn run_basic_sim(matches: &ArgMatches) -> Result<(), String> {
                 LocalNetworkParams {
                     validator_count: total_validator_count,
                     node_count,
+                    extra_nodes,
                     proposer_nodes,
                     genesis_delay,
                 },