[docs] optuna variable typo (#14006)
[docs] optuna variable typo (#14006)

* fix variable name typo

* align
pcmoritz/ray-1,pcmoritz/ray-1,ray-project/ray,pcmoritz/ray-1,pcmoritz/ray-1,ray-project/ray,pcmoritz/ray-1,pcmoritz/ray-1,ray-project/ray,ray-project/ray,ray-project/ray,pcmoritz/ray-1,ray-project/ray,pcmoritz/ray-1,ray-project/ray,ray-project/ray