Raise `NotImplementedError` instead of `NotImplemented` in `test/test_importlib/test_discover.py`

# Bug report

### Bug description:

Code [here](https://github.com/python/cpython/blob/main/Lib/test/test_importlib/test_discover.py#L14C14):
```python
raise NotImplemented
```
Should be `NotImplementedError`


### CPython versions tested on:

CPython main branch

### Operating systems tested on:

_No response_


### Linked PRs
* gh-146661