Rust 1.54.0 lints (#2483)

## Issue Addressed

N/A

## Proposed Changes

- Removing a bunch of unnecessary references
- Updated `Error::VariantError` to `Error::Variant`
- There were additional enum variant lints that I ignored, because I thought our variant names were fine
- removed `MonitoredValidator`'s `pubkey` field, because I couldn't find it used anywhere. It looks like we just use the string version of the pubkey (the `id` field) if there is no index

## Additional Info



Co-authored-by: realbigsean <seananderson33@gmail.com>

beacon_node/network/src/sync/range_sync/batch.rs

@@ -126,7 +126,7 @@ impl<T: EthSpec> BatchInfo<T> {
             BatchState::Downloading(peer_id, _, _)
             | BatchState::AwaitingProcessing(peer_id, _)
             | BatchState::Processing(Attempt { peer_id, .. })
-            | BatchState::AwaitingValidation(Attempt { peer_id, .. }) => Some(&peer_id),
+            | BatchState::AwaitingValidation(Attempt { peer_id, .. }) => Some(peer_id),
             BatchState::Poisoned => unreachable!("Poisoned batch"),
         }
     }