Grascale Example in Readme not working

[Grascale Example](https://github.com/kornia/kornia-rs/tree/main?tab=readme-ov-file#examples-image-processing) was not Updated. While running the example causing  multiple  compilation issues

> error[E0603]: enum `InterpolationMode` is private

> error[E0609]: no field `data` on type `kornia::kornia_image::Image<u8, 3>`

