libp2p upgrade + gossipsub interval fix (#3012)

## Issue Addressed
Lighthouse gossiping late messages

## Proposed Changes
Point LH to our fork using tokio interval, which 1) works as expected 2) is more performant than the previous version that actually worked as expected
Upgrade libp2p 

## Additional Info
https://github.com/libp2p/rust-libp2p/issues/2497

beacon_node/network/src/service.rs

@@ -11,7 +11,7 @@ use futures::channel::mpsc::Sender;
 use futures::future::OptionFuture;
 use futures::prelude::*;
 use lighthouse_network::{
-    open_metrics_client::registry::Registry, MessageAcceptance, Service as LibP2PService,
+    prometheus_client::registry::Registry, MessageAcceptance, Service as LibP2PService,
 };
 use lighthouse_network::{
     rpc::{GoodbyeReason, RPCResponseErrorCode, RequestId},