Remove the duplicated code

Author: JuliaHa0902

src/components/Header/Header.jsx

@@ -160,7 +160,6 @@ export function Header(props) {
   const [hasProfileLoaded, setHasProfileLoaded] = useState(false);
   const dismissalKey = `lastDismissed_${userId}`;
   const [lastDismissed, setLastDismissed] = useState(localStorage.getItem(dismissalKey));
-   const [isAckLoading, setIsAckLoading] = useState(false);
   const unreadNotifications = props.notification?.unreadNotifications; // List of unread notifications
   const dispatch = useDispatch();
   const history = useHistory();