Client.get_versions(check=True) not behaving as expected from docs

The documentation in question

```
raise ValueError if all required & optional packages do not match
```

A quick look at the [tests](https://github.com/dask/distributed/blob/e31bc264dbb14be26e64693210e0eb5563440e89/distributed/tests/test_versions.py) around this feature and I don't see any `with pytest.raises` blocks i'd expect.

From looking at`error_message` https://github.com/dask/distributed/blob/e31bc264dbb14be26e64693210e0eb5563440e89/distributed/versions.py#L156-L165)

The 'error' category will never have anything added to it.

Having the ability to raise an exception and not just a warning is valuable and a little easier to think about than catching the warnings.