fix clippy warning

nghe-api/src/lib.rs

@@ -1,5 +1,5 @@
 #![feature(adt_const_params)]
-#![feature(const_option, const_mut_refs)]
+#![feature(const_option)]
 
 pub mod auth;
 pub mod common;

nghe-backend/src/lib.rs

@@ -1,6 +1,5 @@
 #![feature(adt_const_params)]
 #![feature(anonymous_lifetime_in_impl_trait)]
-#![feature(const_mut_refs)]
 #![feature(iterator_try_collect)]
 #![feature(let_chains)]
 #![feature(try_blocks)]

nghe-backend/src/main.rs

@@ -1,5 +1,3 @@
-#![feature(const_mut_refs)]
-
 use nghe_api::constant;
 use nghe_backend::{build, config, migration};
 use tracing_subscriber::layer::SubscriberExt;