updated requirements for future distributed tests run

[aovladi]

expecttest is a required module by torch/testing/_internal/common_utils.py, which I need in future to pass CI checks.
This PR adds expecttest into requirements-devel.txt

I've tried a to install torchdistx from source with the updated requirements-devel.txt and installation is successful existing tests work.

Check list:

• Was this discussed and approved via a GitHub issue? (not for typos or docs)
• Did you read the contributor guideline?
• Did you make sure that your PR does only one thing instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary) - Not necessary
• Did you write any new necessary tests? - Not necessary
• Did you verify new and existing tests pass locally with your changes?
• Did you update the CHANGELOG? (not for typos, docs, or minor internal changes)

[rohan-varma]

Thanks!

cc @cbalioglu as FYI

[cbalioglu]

LGTM!