Rollup merge of #132413 - lolbinarycat:offset_of_nested-docs, r=workingjubilee

update offset_of! docs to reflect the stabilization of nesting

this seems to have been missed.

library/core/src/mem/mod.rs

@@ -1254,11 +1254,9 @@ impl<T> SizedTypeProperties for T {}
 ///
 /// Nested field accesses may be used, but not array indexes.
 ///
-/// Enum variants may be traversed as if they were fields. Variants themselves do
-/// not have an offset.
-///
-/// However, on stable only a single field name is supported, which blocks the use of
-/// enum support.
+/// If the nightly-only feature `offset_of_enum` is enabled,
+/// variants may be traversed as if they were fields.
+/// Variants themselves do not have an offset.
 ///
 /// Visibility is respected - all types and fields must be visible to the call site:
 ///