"batchSize" was set but never used (#32294)
Summary:
fixes a compiler warning:
```
torch/aten/src/ATen/native/cuda/MaxUnpooling.cu.cc(402):
warning: variable "batchSize" was set but never used
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/32294
Differential Revision: D19697277
Pulled By: ezyang
fbshipit-source-id: b9821be325826dc4785cad7994803b54f1711a0c
