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>

lcli/src/parse_ssz.rs

@@ -30,7 +30,7 @@ pub fn run_parse_ssz<T: EthSpec>(matches: &ArgMatches) -> Result<(), String> {
 }
 
 fn decode_and_print<T: Decode + Serialize>(bytes: &[u8]) -> Result<(), String> {
-    let item = T::from_ssz_bytes(&bytes).map_err(|e| format!("SSZ decode failed: {:?}", e))?;
+    let item = T::from_ssz_bytes(bytes).map_err(|e| format!("SSZ decode failed: {:?}", e))?;
 
     println!(
         "{}",