Mark gate as incomplete

Author: Jules-Bertholet

compiler/rustc_feature/src/unstable.rs

@@ -534,7 +534,7 @@ declare_features! (
     /// Allows the `#[must_not_suspend]` attribute.
     (unstable, must_not_suspend, "1.57.0", Some(83310)),
     /// Make `mut` not reset the binding mode on edition >= 2024.
-    (unstable, mut_preserve_binding_mode_2024, "CURRENT_RUSTC_VERSION", Some(123076)),
+    (incomplete, mut_preserve_binding_mode_2024, "CURRENT_RUSTC_VERSION", Some(123076)),
     /// Allows `mut ref` and `mut ref mut` identifier patterns.
     (incomplete, mut_ref, "CURRENT_RUSTC_VERSION", Some(123076)),
     /// Allows using `#[naked]` on functions.