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>

account_manager/src/common.rs

@@ -19,7 +19,7 @@ pub fn read_mnemonic_from_cli(
             .map_err(|e| format!("Unable to read {:?}: {:?}", path, e))
             .and_then(|bytes| {
                 let bytes_no_newlines: PlainText = strip_off_newlines(bytes).into();
-                let phrase = from_utf8(&bytes_no_newlines.as_ref())
+                let phrase = from_utf8(bytes_no_newlines.as_ref())
                     .map_err(|e| format!("Unable to derive mnemonic: {:?}", e))?;
                 Mnemonic::from_phrase(phrase, Language::English).map_err(|e| {
                     format!(