Uninstall PyTorch after testing on non-ephemeral Windows runners (#97285)
Per title, I suspect that having a leftover PyTorch built from CUDA 11.7 installed in non-ephemeral Windows runners could cause some flakiness on Windows CUDA 11.8 jobs also running on the same type of runners, for example `win-vs2019-cuda11.8-py3` in https://hud.pytorch.org/pytorch/pytorch/commit/5d3c347bf6f0b86c96a1fe541db5d4f9586c8840 failed with a PATH error:
```
nvrtc: error: failed to open nvrtc-builtins64_117.dll.
Make sure that nvrtc-builtins64_117.dll is installed correctly.
```
This also cleans up the dead code about `pytorch_env_restore.bat` under `ci_scripts` temp directory. This directory is cleaned up always by [teardown-win](https://github.com/pytorch/pytorch/blob/master/.github/actions/teardown-win/action.yml#L33). So the bat script will never be there for the next job anyway. As Windows test jobs are doing fine, proving that we don't need this adhoc script anymore.
### Testing
https://github.com/pytorch/pytorch/actions/runs/4485931686/jobs/7888513795
Pull Request resolved: https://github.com/pytorch/pytorch/pull/97285
Approved by: https://github.com/seemethere
