refactor: optimize import and last_tweet_id var

src/util.rs

@@ -1,11 +1,6 @@
-// std
 use std::error::Error;
 use crate::ScootalooError;
-
-// reqwest
 use reqwest::Url;
-
-// tokio
 use tokio::{
     io::copy,
     fs::{File, create_dir_all},