[DataPipe] Fixing interface generation in setup.py (#87081)
Based on the artifact generated on this [page](https://hud.pytorch.org/pr/87081), I downloaded [[s3] linux-focal-py3.7-clang7-asan/artifacts.zip](https://gha-artifacts.s3.amazonaws.com/pytorch/pytorch/3266430083/linux-focal-py3.7-clang7-asan/artifacts.zip) (1.14 GB) and unpacked it. `torch.utils.data.datapipes.datapipe.pyi` does exist. I believe this means the file should be part of the distribution.
I also did `wheel unpack ***.whl` to confirm the existence of the file.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/87081
Approved by: https://github.com/ejguan
