update renamed lint that was moved into rustc

Cargo.toml

@@ -4,6 +4,7 @@ members = [
     "cstree-derive",
     "test_suite",
 ]
+resolver = "2"
 
 [workspace.package]
 edition = "2021"
@@ -15,7 +16,7 @@ authors = [
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/domenicquirl/cstree"
 readme = "README.md"
-rust-version = "1.68"
+rust-version = "1.71"
 
 [profile.release]
 debug = true

cstree/tests/it/sendsync.rs

@@ -149,7 +149,7 @@ fn drop_send() {
 
 #[test]
 #[cfg_attr(miri, ignore)]
-#[allow(clippy::drop_ref)]
+#[allow(dropping_references)]
 fn drop_sync() {
     let tree = two_level_tree();
     let tree = build_tree::<()>(&tree);