Switch note to warning.

Author: ehuss

src/expressions/array-expr.md

@@ -26,10 +26,14 @@ If `b` is 0, the constant item is not evaluated at all. For expressions that
 are not a constant item, it is evaluated exactly once, and then the result is
 copied `b` times.
 
-> **Note:** In the case where `b` is 0, and `a` is a non-constant item, there
-> is currently a bug in `rustc` where the value `a` is evaluated but not
-> dropped, thus causing a leak. See [issue
-> #74836](https://github.com/rust-lang/rust/issues/74836).
+<div class="warning">
+
+Warning: In the case where `b` is 0, and `a` is a non-constant item, there is
+currently a bug in `rustc` where the value `a` is evaluated but not dropped,
+thus causing a leak. See [issue
+#74836](https://github.com/rust-lang/rust/issues/74836).
+
+</div>
 
 ```rust
 [1, 2, 3, 4];