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

testing/ef_tests/src/cases/common.rs

@@ -1,7 +1,6 @@
 use serde::Deserialize;
 use ssz::Encode;
 use ssz_derive::{Decode, Encode};
-use std::convert::TryFrom;
 use std::fmt::Debug;
 use tree_hash::TreeHash;
 use types::ForkName;