Reduce test size for max_pool (#65336)
Summary:
Fixe OOM in slow gradcheck tests.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/65336
Reviewed By: malfet
Differential Revision: D31059007
Pulled By: albanD
fbshipit-source-id: 2dd6967d88663558e37f8c0836ad33333c92dfb5
