Rollup merge of rust-lang#95791 - oconnor663:doc_comment, r=thomcc

hide an #[allow] directive from the Arc::new_cyclic doc example

A minor docs cleanup.

Author: Dylan-DPC

library/alloc/src/sync.rs

@@ -369,7 +369,7 @@ impl<T> Arc<T> {
     ///
     /// # Example
     /// ```
-    /// #![allow(dead_code)]
+    /// # #![allow(dead_code)]
     /// use std::sync::{Arc, Weak};
     ///
     /// struct Gadget {