Unnecessary warning is generated on `fieldsSet`

Having a schema like this

enum PokemonType {
   FIRE
   WATER
   ELECTRIC
   GRASS
}

type Query {
   getAllPokemonTypes: [PokemonType!]!
}

The plugin generates a GetAllPokemonTypesGraphQLQuery class containing a warning inside the Builder

public static class Builder {
    private Set<String> fieldsSet = new HashSet<>();
    ....
  }

The value of the field GetAllPokemonTypesGraphQLQuery.Builder.fieldsSet is not used

I believe it happens always when the return value of a query is a [xxx!]!, whether is an enum or type.

It's not very important but it would be nice to remove it, so we can keep the generated code warning-free!

Reproduce the issue with the provided GraphQL schema and inspect the generated GetAllPokemonTypesGraphQLQuery.Builder, focusing on the fieldsSet declaration and the generation path for non-null list return values. Done means the generated Builder no longer contains an unused fieldsSet warning for this schema, while preserving query generation.