Small fix: documentation of Tensor::stack

[PonasKovas]

Changes

Changed the documentation on Tensor::stack function to be less confusing and misleading.

use burn::{
    backend::NdArray,
    tensor::{Int, Tensor},
};

fn main() {
    type B = NdArray;

    let v1 = Tensor::<B, 1, Int>::arange(2..5);
    let v2 = Tensor::<B, 1, Int>::arange(1..4);

    // Runtime error, even though `dim: 2` falls in the range of `0..=D2`.
    dbg!(Tensor::stack::<2>(vec![v1, v2], 2));
}

This probably must have been a simple typo or misunderstanding, since we index dimensions from 0, so if your tensor has D2 dimensions, the highest you can index is D2-1.

[louisfd]

Thank you, you're right about that