Downgrade libp2p and gosispsub (#1358)

Downgrades libp2p and the gossipsub updates. 

This looks to resolve the CPU usage issue we have been seeing. 

The root cause is likely inside the latest gossipsub updates, which will be addressed in a later PR

beacon_node/eth2_libp2p/src/config.rs

@@ -94,8 +94,8 @@ impl Default for Config {
         let gs_config = GossipsubConfigBuilder::new()
             .max_transmit_size(GOSSIP_MAX_SIZE)
             .heartbeat_interval(Duration::from_secs(1))
-            .history_length(385) // A heartbeat is 1 second. We want to keep an epoch worth of history,
             .manual_propagation() // require validation before propagation
+            .no_source_id()
             .message_id_fn(gossip_message_id)
             .build();