Tweak wording in header about unsafe extern

Since we're adding `unsafe extern` in this release, saying "safe items
with unsafe extern" rather than "safe items in unsafe extern" here
sounds more right to my ear.

posts/2024-10-17-Rust-1.82.0.md

@@ -168,7 +168,7 @@ fn main() {
 
 The native syntax makes it more clear that the operand expression of these operators is interpreted as a [place expression](https://www.ralfj.de/blog/2024/08/14/places.html). It also avoids the term "address-of" when referring to the action of creating a pointer. A pointer is [more than just an address](https://rust-lang.github.io/rfcs/3559-rust-has-provenance.html), so Rust is moving away from terms like "address-of" that reaffirm a false equivalence of pointers and addresses.
 
-### Safe items in `unsafe extern`
+### Safe items with `unsafe extern`
 
 Rust code can use functions and statics from foreign code.  The type signatures of these foreign items are provided in `extern` blocks.  Historically, all items within `extern` blocks have been unsafe to call, but we didn't have to write `unsafe` anywhere on the `extern` block itself.