housekeeping(server): fixed clippy warns

server/crates/arbiter-server/tests/keyholder/concurrency.rs

@@ -1,11 +1,10 @@
 use std::collections::{HashMap, HashSet};
 
+use arbiter_crypto::safecell::{SafeCell, SafeCellHandle as _};
 use arbiter_server::{
     actors::keyholder::{CreateNew, Error, KeyHolder},
     db::{self, models, schema},
-   
 };
-use arbiter_crypto::{authn::{self, format_challenge, CLIENT_CONTEXT}, safecell::{SafeCell, SafeCellHandle as _}};
 
 use diesel::{ExpressionMethods as _, QueryDsl, SelectableHelper, dsl::sql_query};
 use diesel_async::RunQueryDsl;