refactor(clippy): adapt to new lints

src/flatten.rs

@@ -31,7 +31,7 @@ fn internal<'a>(
 
         result.push(Flattened {
             item,
-            identifier: child_identifier.to_vec(),
+            identifier: child_identifier.clone(),
         });
 
         if opened.contains(&child_identifier) {

src/lib.rs

@@ -34,7 +34,7 @@ impl Default for TreeState {
 
 impl TreeState {
     pub fn selected(&self) -> Vec<usize> {
-        self.selected.to_owned()
+        self.selected.clone()
     }
 
     pub fn select<I>(&mut self, identifier: I)