adjust FIXME comment

Author: matklad

src/inline_lazy.rs

@@ -15,7 +15,7 @@ use self::std::sync::Once;
 #[allow(deprecated)]
 pub use self::std::sync::ONCE_INIT;
 
-// FIXME: Replace Option<T> with MaybeInitialized<T>
+// FIXME: Replace Option<T> with MaybeUninit<T> (stable since 1.36.0)
 pub struct Lazy<T: Sync>(Cell<Option<T>>, Once);
 
 impl<T: Sync> Lazy<T> {