Fix compiler warnings in PR rust-bitcoin#291

Author: SarcasticNastik

src/policy/mod.rs

@@ -442,8 +442,8 @@ mod tests {
             let descriptor = policy.compile_tr(Some(unspendable_key.clone())).unwrap();
 
             let mut sorted_policy_prob = node_policies
-                .into_iter()
-                .zip(node_probabilities.into_iter())
+                .iter()
+                .zip(node_probabilities.iter())
                 .collect::<Vec<_>>();
             sorted_policy_prob.sort_by(|a, b| (a.1).partial_cmp(&b.1).unwrap());
             let sorted_policies = sorted_policy_prob