Fix `functional.max_poolNd` warning spam in the CI
Fixes https://github.com/pytorch/pytorch/issues/71257.
Warnings have been removed, please see [this](https://github.com/pytorch/pytorch/pull/71258#issuecomment-1058503649) comment.
cc: @Lezcano @jbschlosser @zou3519
Pull Request resolved: https://github.com/pytorch/pytorch/pull/71258
Approved by: https://github.com/Lezcano, https://github.com/jbschlosser
