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>

consensus/state_processing/src/genesis.rs

@@ -34,7 +34,7 @@ pub fn initialize_beacon_state_from_eth1<T: EthSpec>(
             .push_leaf(deposit.data.tree_hash_root())
             .map_err(BlockProcessingError::MerkleTreeError)?;
         state.eth1_data_mut().deposit_root = deposit_tree.root();
-        process_deposit(&mut state, &deposit, spec, true)?;
+        process_deposit(&mut state, deposit, spec, true)?;
     }
 
     process_activations(&mut state, spec)?;