Add release note for new ambiguous_wide_pointer_comparisons lint

Author: carols10cents

RELEASES.md

@@ -8,6 +8,7 @@ Language
 - [Document Rust ABI compatibility between various types](https://github.com/rust-lang/rust/pull/115476/)
 - [Also: guarantee that char and u32 are ABI-compatible](https://github.com/rust-lang/rust/pull/118032/)
 - [Warn against ambiguous wide pointer comparisons](https://github.com/rust-lang/rust/pull/117758/)
+- [Add lint `ambiguous_wide_pointer_comparisons` that supersedes `clippy::vtable_address_comparisons`](https://github.com/rust-lang/rust/pull/117758)
 
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