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>

validator_client/src/initialized_validators.rs

@@ -33,7 +33,7 @@ const USE_STDIN: bool = false;
 pub enum Error {
     /// Refused to open a validator with an existing lockfile since that validator may be in-use by
     /// another process.
-    LockfileError(LockfileError),
+    Lockfile(LockfileError),
     /// The voting public key in the definition did not match the one in the keystore.
     VotingPublicKeyMismatch {
         definition: Box<PublicKey>,
@@ -66,7 +66,7 @@ pub enum Error {
 
 impl From<LockfileError> for Error {
     fn from(error: LockfileError) -> Self {
-        Self::LockfileError(error)
+        Self::Lockfile(error)
     }
 }
 
@@ -456,7 +456,7 @@ impl InitializedValidators {
                         read_password(path).map_err(Error::UnableToReadVotingKeystorePassword)?
                     } else {
                         let keystore = open_keystore(voting_keystore_path)?;
-                        unlock_keystore_via_stdin_password(&keystore, &voting_keystore_path)?
+                        unlock_keystore_via_stdin_password(&keystore, voting_keystore_path)?
                             .0
                             .as_ref()
                             .to_vec()