feat(downloads): Convert DownloadThreadControlFlag to AtomicBool

Also ran cargo fmt & cargo clipy

Signed-off-by: quexeky <git@quexeky.dev>

src-tauri/src/downloads/download_commands.rs

@@ -1,7 +1,4 @@
-use std::{
-    borrow::Borrow,
-    sync::{Arc, Mutex},
-};
+use std::sync::{Arc, Mutex};
 
 use log::info;
 use rayon::spawn;