Resolve iter_overeager_cloned clippy lint

    warning: called `cloned().next()` on an `Iterator`. It may be more efficient to call `next().cloned()` instead
       --> src/main.rs:450:30
        |
    450 |         if let Some(first) = set.iter().cloned().next() {
        |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `set.iter().next().cloned()`
        |
        = note: `#[warn(clippy::iter_overeager_cloned)]` on by default
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#iter_overeager_cloned

src/main.rs

@@ -447,7 +447,7 @@ fn try_main(log: &mut Log) -> Result<()> {
 
     let now = Utc::now();
     for set in stars.values_mut() {
-        if let Some(first) = set.iter().cloned().next() {
+        if let Some(first) = set.iter().next() {
             set.insert(Star {
                 time: first.time - Duration::seconds(1),
                 node: Default::default(),