update gossipsub to the latest upstream revision (#7130)

I feel it's preferable to do this explicitly by updating the revision on `Cargo.toml` rather than implicitly by letting `Cargo.lock` control the revision of the branch.

beacon_node/lighthouse_network/src/service/mod.rs

@@ -996,7 +996,7 @@ impl<E: EthSpec> Network<E> {
                         }
                     }
 
-                    if let PublishError::InsufficientPeers = e {
+                    if let PublishError::NoPeersSubscribedToTopic = e {
                         self.gossip_cache.insert(topic, message_data);
                     }
                 }