Fix artifact path for cuda extension test in push CI
# What does this PR do?

Fix artifact path for cuda extension test in push CI

### More details
In #17335, `working-director` is updated (a fix) for (single-gpu) cuda extension test, but the artifact path was not updated, which leads to strange slack report.

```bash
      - name: Run all non-slow selected tests on GPU
        working-directory: /workspace/transformers
        ...
```