Fix Rust beta compiler errors 1.78.0-beta.1 (#5439)

* remove redundant imports

* fix test

* contains key

* fmt

* Merge branch 'unstable' into fix-beta-compiler

slasher/src/array.rs

@@ -7,9 +7,7 @@ use flate2::bufread::{ZlibDecoder, ZlibEncoder};
 use serde::{Deserialize, Serialize};
 use std::borrow::Borrow;
 use std::collections::{btree_map::Entry, BTreeMap, HashSet};
-use std::convert::TryFrom;
 use std::io::Read;
-use std::iter::Extend;
 use std::sync::Arc;
 use types::{AttesterSlashing, Epoch, EthSpec, IndexedAttestation};
 

slasher/src/database/lmdb_impl.rs

@@ -3,15 +3,12 @@
 use crate::{
     config::MEGABYTE,
     database::{
-        interface::{Key, OpenDatabases, Value},
+        interface::{Key, Value},
         *,
     },
-    Config, Error,
 };
 use lmdb::{Cursor as _, DatabaseFlags, Transaction, WriteFlags};
 use lmdb_sys::{MDB_FIRST, MDB_GET_CURRENT, MDB_LAST, MDB_NEXT};
-use std::borrow::Cow;
-use std::marker::PhantomData;
 use std::path::PathBuf;
 
 #[derive(Debug)]