add 3d input and output shapes to maxpool documentation (#61310)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/61310
Test Plan: Imported from OSS
Reviewed By: jbschlosser
Differential Revision: D29737516
Pulled By: migeed-z
fbshipit-source-id: eb6964f6808b8ae05d4d3852a5162dc66930cd64
