fix some pedantic clippy lints that make sense

- clippy::redundant-closure-for-method-calls
- clippy::explicit-iter-loop

aoc2019/src/day14.rs

@@ -79,7 +79,7 @@ fn get_ore_cost(
 
         let needed = quantity - in_stock;
         let num_reactions = (needed + recipe.produced - 1) / recipe.produced;
-        for elem in recipe.elems.iter() {
+        for elem in &recipe.elems {
             total += get_ore_cost(
                 elem.name.clone(),
                 elem.amount * num_reactions,