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/ssz_derive/src/lib.rs

@@ -17,7 +17,7 @@ fn get_serializable_named_field_idents(struct_data: &syn::DataStruct) -> Vec<&sy
         .fields
         .iter()
         .filter_map(|f| {
-            if should_skip_serializing(&f) {
+            if should_skip_serializing(f) {
                 None
             } else {
                 Some(match &f.ident {
@@ -36,7 +36,7 @@ fn get_serializable_field_types(struct_data: &syn::DataStruct) -> Vec<&syn::Type
         .fields
         .iter()
         .filter_map(|f| {
-            if should_skip_serializing(&f) {
+            if should_skip_serializing(f) {
                 None
             } else {
                 Some(&f.ty)