Enums classes are missing in types/__init__.py`

This results in the enums being omitted in the generated `types` docs.

Dataproc has a [`Component`](https://github.com/googleapis/python-dataproc/blob/master/google/cloud/dataproc_v1/types/shared.py) enum that isn't present in the [`types/__init__.py`](https://github.com/googleapis/python-dataproc/blob/master/google/cloud/dataproc_v1/types/__init__.py#L125)