Remove unnecessary cloning in block sync

Author: foriequal0

sync/src/block/extension.rs

@@ -572,11 +572,8 @@ pub enum Event {
 impl Extension {
     fn new_headers(&mut self, imported: Vec<BlockHash>, enacted: Vec<BlockHash>, retracted: Vec<BlockHash>) {
         if let State::Full = self.state {
-            let peer_ids: Vec<_> = self.header_downloaders.keys().cloned().collect();
-            for id in peer_ids {
-                if let Some(peer) = self.header_downloaders.get_mut(&id) {
-                    peer.mark_as_imported(imported.clone());
-                }
+            for peer in self.header_downloaders.values_mut() {
+                peer.mark_as_imported(imported.clone());
             }
             let mut headers_to_download: Vec<_> = enacted
                 .into_iter()