Drop the mention of extern edition differences

Author: t5kd

library/std/src/keyword_docs.rs

@@ -381,9 +381,7 @@ mod enum_keyword {}
 /// lazy_static;`. The other use is in foreign function interfaces (FFI).
 ///
 /// `extern` is used in two different contexts within FFI. The first is in the form of external
-/// blocks, for declaring function interfaces that Rust code can call foreign code by. Starting
-/// with Rust 2024, external blocks must be marked as `unsafe`. In earlier editions, use of
-/// the `unsafe` keyword remains optional.
+/// blocks, for declaring function interfaces that Rust code can call foreign code by.
 ///
 /// ```rust ignore
 /// #[link(name = "my_c_library")]