Fix Rust beta compiler errors 1.78.0-beta.1 (#5439)

* remove redundant imports

* fix test

* contains key

* fmt

* Merge branch 'unstable' into fix-beta-compiler

beacon_node/network/src/sync/manager.rs

@@ -57,7 +57,6 @@ use lighthouse_network::types::{NetworkGlobals, SyncState};
 use lighthouse_network::SyncInfo;
 use lighthouse_network::{PeerAction, PeerId};
 use slog::{crit, debug, error, info, trace, warn, Logger};
-use std::boxed::Box;
 use std::ops::IndexMut;
 use std::ops::Sub;
 use std::sync::Arc;