Refactor c10d and dist aliases for torch.distributed (#59456)
Summary:
**Overview:**
This consolidates `c10d` and `dist` to only `dist` as the alias for `torch.distributed` in `test_store.py`. Both aliases were used most likely due to incremental additions to the test file and not intentional.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59456
Test Plan:
```
python test/distributed/test_store.py
```
Reviewed By: agolynski
Differential Revision: D28910169
Pulled By: andwgu
fbshipit-source-id: f830dead29e9de48aaf2845dfa5861c9cccec15d
