Evidence

I remember seeing this commit that specialized StepBy for ops::Range and today when looking back at the library's source code I saw that the specialization is gone.
Here's the specialization commit merged: 95979dc
Here's the current code for StepBy::next(): https://github.com/rust-lang/rust/blob/master/library/core/src/iter/adapters/step_by.rs#L34

Why was this specialization removed and can we add it back?