Update if-let-expressions.md (#540)

* Update if-let-expressions.md

add a note about let-else expressions.  Closes #536

* Remove old mention of let-else

* Indent code block to match the bullet point

---------

Co-authored-by: Martin Geisler <martin@geisler.net>

src/control-flow/if-let-expressions.md

@@ -19,8 +19,21 @@ Rust.
 <details>
 
 * `if let` can be more concise than `match`, e.g., when only one case is interesting. In contrast, `match` requires all branches to be covered.
-    * For the similar use case consider demonstrating a newly stabilized [`let else`](https://github.com/rust-lang/rust/pull/93628) feature.
 * A common usage is handling `Some` values when working with `Option`.
 * Unlike `match`, `if let` does not support guard clauses for pattern matching.
+* Since 1.65, a similar [let-else](https://doc.rust-lang.org/rust-by-example/flow_control/let_else.html) construct allows to do a destructuring assignment, or if it fails, have a non-returning block branch (panic/return/break/continue):
+
+   ```rust,editable
+   fn main() {
+       println!("{:?}", second_word_to_upper("foo bar"));
+   }
+    
+   fn second_word_to_upper(s: &str) -> Option<String> {
+       let mut it = s.split(' ');
+       let (Some(_), Some(item)) = (it.next(), it.next()) else {
+           return None;
+       };
+       Some(item.to_uppercase())
+   }
 
 </details>