2024: Add note about never_type_fallback_flowing_into_unsafe lint level.

src/rust-2024/never-type-fallback.md

@@ -5,6 +5,9 @@
 ## Summary
 
 - Never type (`!`) to any type ("never-to-any") coercions fall back to never type (`!`) rather than to unit type (`()`).
+- The [`never_type_fallback_flowing_into_unsafe`] lint is now `deny` by default.
+
+[`never_type_fallback_flowing_into_unsafe`]: ../../rustc/lints/listing/warn-by-default.html#never-type-fallback-flowing-into-unsafe
 
 ## Details
 
@@ -54,6 +57,10 @@ In some cases your code might depend on the fallback type being `()`, so this ca
 
 [coercion site]: ../../reference/type-coercions.html#coercion-sites
 
+### `never_type_fallback_flowing_into_unsafe`
+
+The default level of the [`never_type_fallback_flowing_into_unsafe`] lint has been raised from `warn` to `deny` in the 2024 Edition. This lint helps detect a particular interaction with the fallback to `!` and `unsafe` code which may lead to undefined behavior. See the link for a complete description.
+
 ## Migration
 
 There is no automatic fix, but there is automatic detection of code that will be broken by the edition change.  While still on a previous edition you will see warnings if your code will be broken.