How to make a documentation for the super enum without sharing it with the sub enum?

If I do this and run `cargo doc`, the description of `SuperEnum` would be appended to the description of `SubEnum`.

```rust
/// super enum.
#[subenum(SubEnum(doc = "sub enum."))]
pub enum SuperEnum {
    #[subenum(SubEnum)]
    Foo,
}
```

The docs would show this:

```text
SuperEnum — super enum.
SubEnum — sub enum. super enum.
```

This is not a desired behavior.