Don’t make multiple centroid iterations on the same leaf

[irevoire]

arroy/src/distance/mod.rs

Line 136 in 4f193fd

let node_k = leafs.choose(rng)?.unwrap();

Here we should remove the selected leaf from the list of possible leafs.
That means, when we have less than 200 leafs to split we can exit early.
It’ll impact relevancy but I’m pretty sure it won’t have a negative impact