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>

crypto/eth2_wallet/src/wallet.rs

@@ -138,7 +138,7 @@ impl Wallet {
         name: String,
         nextaccount: u32,
     ) -> Result<Self, Error> {
-        let (cipher_text, checksum) = encrypt(&seed, &password, &kdf, &cipher)?;
+        let (cipher_text, checksum) = encrypt(seed, password, &kdf, &cipher)?;
 
         Ok(Self {
             json: JsonWallet {
@@ -192,7 +192,7 @@ impl Wallet {
         // incrementing `nextaccount`.
         let derive = |key_type: KeyType, password: &[u8]| -> Result<Keystore, Error> {
             let (secret, path) =
-                recover_validator_secret(&self, wallet_password, self.json.nextaccount, key_type)?;
+                recover_validator_secret(self, wallet_password, self.json.nextaccount, key_type)?;
 
             let keypair = keypair_from_secret(secret.as_bytes())?;