Outdated ref to binary search pull

[TheIronBorn]

ordsearch/README.md

Lines 46 to 48 in 8315c47

 trend is that `ordsearch` is faster when `n` is smaller and `T` is larger. You may also want to 
 compare with the pending Rust PR "[Improve SliceExt::binary_search 
 performance](https://github.com/rust-lang/rust/pull/45333)".