Incorrect Multilingual arc implementation

[hynky1999]

The okapi translated arc uses preprocessing for no reason (likely oversight as the preprocessing if for hellaswag). I am not sure if it destroys some instructions, but I don't think there is any preprocessing needed.

Line in question:
https://github.com/EleutherAI/lm-evaluation-harness/blob/main/lm_eval/tasks/okapi/arc_multilingual/utils.py#L6