[BE] Prevent pytest from thinking this class defines any tests (#100949)
Fixes the error:
```
/var/lib/jenkins/pytorch/test/inductor/test_torchinductor.py:6021: PytestCollectionWarning: cannot collect test class 'TestFailure' because it has a __init__ constructor (from: test/inductor/test_torchinductor.py)
class TestFailure:
```
It does so by marking the class as not actually being a test class, despite it's name starting with `Test`.
For more details see: https://stackoverflow.com/a/72465142/21539
Pull Request resolved: https://github.com/pytorch/pytorch/pull/100949
Approved by: https://github.com/huydhn
