feat: Enable Nix 2.33 APIs for pre-release testing/validation

Pre-release versions (2.33.0pre) now enable 2.33 APIs, allowing development
and integration testing before the stable release. Tests remain disabled for
2.33 until stable to avoid blocking on unrelated pre-release issues.

nix-bindings-store/src/derivation.rs

@@ -1,4 +1,4 @@
-#![cfg(nix_at_least = "2.33")]
+#![cfg(nix_at_least = "2.33.0pre")]
 
 use nix_bindings_bindgen_raw as raw;
 use std::ptr::NonNull;