fix type error in hipify_python.py (#66164)
Summary:
- [x] Fixed the Pyre type checking errors in `torch/utils/hipify/hipify_python.py`:
```
torch/utils/hipify/hipify_python.py:196:8 Incompatible variable type [9]: clean_ctx is declared to have type `GeneratedFileCleaner` but is used as type `None`.
torch/utils/hipify/hipify_python.py:944:4 Incompatible variable type [9]: clean_ctx is declared to have type `GeneratedFileCleaner` but is used as type `None`.
```
Fixing the issue: https://github.com/MLH-Fellowship/pyre-check/issues/78
Pull Request resolved: https://github.com/pytorch/pytorch/pull/66164
Reviewed By: onionymous
Differential Revision: D31411443
Pulled By: 0xedward
fbshipit-source-id: c69f8fb839ad1d5ba5e4a223e1322ae7207e1574
