Fix unused variable warning in DilatedMaxPool3d.cu (#71590)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/71590
Test Plan: Sandcastle
Reviewed By: malfet
Differential Revision: D33692617
fbshipit-source-id: e9663458c8598822d3b022a0623a66a0e8d1fa5f
(cherry picked from commit 692c94ae85ec99ee3494c1df53362231085a3398)
