Fix incorrect reference in internal doc
@@ -339,7 +339,7 @@ impl<'k, W: Write> Struct<'k, W> {
/// If `key` has a magic value [`TEXT_KEY`], then `value` serialized as a
/// [simple type].
///
- /// If `key` has a magic value [`CONTENT_KEY`], then `value` serialized as a
+ /// If `key` has a magic value [`VALUE_KEY`], then `value` serialized as a
/// [content] without wrapping in tags, otherwise it is wrapped in
/// `<${key}>...</${key}>`.
///
