Remove a workaround for a Clippy issue

Remove allow `clippy::arc_with_non_send_sync` as the false positives have been fixed
in Clippy.

src/notification/notifier.rs

@@ -159,12 +159,9 @@ impl<K, V> ThreadPoolRemovalNotifier<K, V> {
             is_shutting_down: Default::default(),
         };
 
-        #[cfg_attr(beta_clippy, allow(clippy::arc_with_non_send_sync))]
-        let state = Arc::new(state);
-
         Self {
             snd,
-            state,
+            state: Arc::new(state),
             thread_pool,
         }
     }

src/sync_base/invalidator.rs

@@ -114,7 +114,6 @@ impl<K, V, S> Invalidator<K, V, S> {
         Self {
             predicates: RwLock::new(HashMap::new()),
             is_empty: AtomicBool::new(true),
-            #[cfg_attr(beta_clippy, allow(clippy::arc_with_non_send_sync))]
             scan_context: Arc::new(ScanContext::new(cache)),
             thread_pool,
         }