Remove 4 unused variables in lp_pool_op.cc (#42329)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/42329
Reviewed By: VitalyFedyunin
Differential Revision: D22850894
Pulled By: mrshenli
fbshipit-source-id: 1e91380a432525b83c0bb0bfef0d5067c767cb67
