remove unused context trait and fix warning

substrate/candidate-agreement/src/bft/accumulator.rs

@@ -22,18 +22,6 @@ use std::hash::Hash;
 
 use super::{Message, LocalizedMessage};
 
-/// Context necessary to execute a round of BFT.
-pub trait Context {
-	/// A full candidate.
-	type Candidate: Clone;
-	/// Unique digest of a proposed candidate (think hash).
-	type Digest: Hash + Eq + Clone;
-	/// Validator ID.
-	type ValidatorId: Hash + Eq;
-	/// A signature.
-	type Signature: Eq + Clone;
-}
-
 /// Justification at a given round.
 #[derive(PartialEq, Eq, Debug, Clone)]
 pub struct Justification<D, S> {

substrate/candidate-agreement/src/table.rs

@@ -284,7 +284,7 @@ impl<C: Context> Table<C> {
 			let candidate = &candidate_data.candidate;
 			match best_candidates.entry(group_id.clone()) {
 				BTreeEntry::Occupied(mut occ) => {
-					let mut candidate_ref = occ.get_mut();
+					let candidate_ref = occ.get_mut();
 					if *candidate_ref < candidate {
 						*candidate_ref = candidate;
 					}