Change #[rustc_as_ptr] description for clarity

Author: gavincrawford

compiler/rustc_feature/src/builtin_attrs.rs

@@ -878,7 +878,7 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     rustc_attr!(
         rustc_as_ptr, Normal, template!(Word), ErrorFollowing,
         EncodeCrossCrate::Yes,
-        "#[rustc_as_ptr] is used to mark functions that implement `as_ptr` or `as_ptr_mut`."
+        "#[rustc_as_ptr] is used to mark functions returning pointers to their inner allocations."
     ),
     rustc_attr!(
         rustc_pass_by_value, Normal, template!(Word), ErrorFollowing,