Ignore unreachable_pub lint

```
warning: unreachable `pub` item
  --> futures-util/src/stream/futures_unordered/mod.rs:25:32
   |
25 | pub use self::iter::{IntoIter, Iter, IterMut, IterPinMut, IterPinRef};
   | ---                            ^^^^
   | |
   | help: consider restricting its visibility: `pub(crate)`
   |
   = help: or consider exporting it for use by other crates
note: the lint level is defined here
  --> futures-util/src/lib.rs:11:5
   |
11 |     unreachable_pub
   |     ^^^^^^^^^^^^^^^

warning: unreachable `pub` item
  --> futures-util/src/stream/futures_unordered/mod.rs:25:38
   |
25 | pub use self::iter::{IntoIter, Iter, IterMut, IterPinMut, IterPinRef};
   | ---                                  ^^^^^^^
   | |
   | help: consider restricting its visibility: `pub(crate)`
   |
   = help: or consider exporting it for use by other crates
```

futures-util/src/stream/futures_unordered/mod.rs

@@ -22,6 +22,7 @@ use futures_task::{FutureObj, LocalFutureObj, LocalSpawn, Spawn, SpawnError};
 mod abort;
 
 mod iter;
+#[allow(unreachable_pub)] // https://github.com/rust-lang/rust/issues/102352
 pub use self::iter::{IntoIter, Iter, IterMut, IterPinMut, IterPinRef};
 
 mod task;