Amend data-carrying enums definition

Author: gnzlbg

reference/src/layout/enums.md

@@ -46,10 +46,10 @@ As in C, discriminant values that are not specified are defined as
 either 0 (for the first variant) or as one more than the prior
 variant.
 
-**Data-carrying enums.** Enums whose variants have fields are called
-"data-carrying" enums. Note that for the purposes of this definition,
-it is not relevant whether those fields are zero-sized. Therefore this
-enum is considered "data-carrying":
+**Data-carrying enums.** Enums with at least one variant with fields are called
+"data-carrying" enums. Note that for the purposes of this definition, it is not
+relevant whether the variant fields are zero-sized. Therefore this enum is
+considered "data-carrying":
 
 ```rust
 enum Foo {