`rayon` is included in the dependency tree even when the `rayon` feature is disabled when `ravif` feature is enabled

[Shnatsel]

This happens in image 0.25.2.

To reproduce:

cargo new img-test
cd img-test
cargo add image --no-default-features --features=default-formats
cargo tree -i rayon

prints:

rayon v1.10.0
├── maybe-rayon v0.1.1
│   └── rav1e v0.7.1
│       └── ravif v0.11.8
│           └── image v0.25.2
│               └── img-test v0.1.0
└── ravif v0.11.8 (*)

[kornelski]

I've added a threading feature to ravif.