Fix module path in user_data documentation example
//!
//! ```ignore
//! #[derive(NativeClass)]
-//! #[inherit(gdnative::Node)]
-//! #[user_data(gdnative::user_data::MutexData<HelloWorld>)]
+//! #[inherit(gdnative::api::Node)]
+//! #[user_data(gdnative::nativescript::user_data::MutexData<HelloWorld>)]
//! struct HelloWorld;
//! ```
//!
