bug: Generating Required Custom Type as Pointer

### What happened?
When I define a custom type as required, it is generated as pointer. For example I have `[FavoriteList!]` in my schema but it generates resolver as `[]*model.FavoriteList`

### What did you expect?
I expect custom model type as not a pointer type, I think it should be `[]model.FavoriteList`

### Minimal graphql.schema and models to reproduce
```graphql
type FavoriteList {
id: Int
}

extend type Query {
favoriteLists: [FavoriteList!]
}
```

```go
func (r *queryResolver) FavoriteLists(ctx context.Context) ([]*model.FavoriteList, error) {
// ...
}
```

### versions
- `go run github.com/99designs/gqlgen version`? - v0.17.40
- `go version`? - 1.21.1