chore: fix clippy warnings (#6466)

tokio-util/src/sync/cancellation_token/tree_node.rs

@@ -206,7 +206,7 @@ fn move_children_to_parent(node: &mut Inner, parent: &mut Inner) {
     for child in std::mem::take(&mut node.children) {
         {
             let mut child_locked = child.inner.lock().unwrap();
-            child_locked.parent = node.parent.clone();
+            child_locked.parent.clone_from(&node.parent);
             child_locked.parent_idx = parent.children.len();
         }
         parent.children.push(child);

tokio-util/src/task/spawn_pinned.rs

@@ -23,7 +23,7 @@ use tokio::task::{spawn_local, JoinHandle, LocalSet};
 ///
 /// ```
 /// use std::rc::Rc;
-/// use tokio::{self, task };
+/// use tokio::task;
 /// use tokio_util::task::LocalPoolHandle;
 ///
 /// #[tokio::main(flavor = "current_thread")]