Appease clippy in Rust 1.70 (#4365)

## Issue Addressed

NA

## Proposed Changes

Fixes some new clippy lints raised after updating to Rust 1.70.

## Additional Info

NA

beacon_node/client/src/builder.rs

@@ -742,7 +742,7 @@ where
 
             runtime_context
                 .executor
-                .spawn_without_exit(async move { server.await }, "http-metrics");
+                .spawn_without_exit(server, "http-metrics");
 
             Some(listen_addr)
         } else {

beacon_node/http_metrics/tests/tests.rs

@@ -38,7 +38,7 @@ async fn returns_200_ok() {
         };
         let (listening_socket, server) = http_metrics::serve(ctx, server_shutdown).unwrap();
 
-        tokio::spawn(async { server.await });
+        tokio::spawn(server);
 
         let url = format!(
             "http://{}:{}/metrics",

beacon_node/lighthouse_network/src/discovery/subnet_predicate.rs

@@ -1,4 +1,4 @@
-///! The subnet predicate used for searching for a particular subnet.
+//! The subnet predicate used for searching for a particular subnet.
 use super::*;
 use crate::types::{EnrAttestationBitfield, EnrSyncCommitteeBitfield};
 use slog::trace;