remove unused/debug header (#82845)
### Description
Missed one of the review comments in https://github.com/pytorch/pytorch/pull/82731 . Namely, to remove an unused `<iostream>` that was used for debugging
### Issue
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### Testing
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Pull Request resolved: https://github.com/pytorch/pytorch/pull/82845
Approved by: https://github.com/Chillee, https://github.com/albanD
