Cleanup our sort usage (#6754)

substrate/primitives/npos-elections/src/lib.rs

@@ -749,7 +749,7 @@ fn do_balancing<AccountId>(
 		e.1 = 0;
 	});
 
-	elected_edges.sort_unstable_by_key(|e|
+	elected_edges.sort_by_key(|e|
 		if let Some(e) = support_map.get(&e.0) { e.total } else { Zero::zero() }
 	);
 

substrate/primitives/npos-elections/src/mock.rs

@@ -264,7 +264,7 @@ pub(crate) fn do_equalize_float<A>(
 		e.1 = 0.0;
 	});
 
-	elected_edges.sort_unstable_by(|x, y|
+	elected_edges.sort_by(|x, y|
 		support_map.get(&x.0)
 			.and_then(|x| support_map.get(&y.0).and_then(|y| x.total.partial_cmp(&y.total)))
 			.unwrap_or(sp_std::cmp::Ordering::Equal)