chore(deps): update dependency google-cloud-dataproc to v0.8.1 (GoogleCloudPlatform#4015)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [google-cloud-dataproc](https://github.com/googleapis/python-dataproc) | patch | `==0.8.0` -> `==0.8.1` |

---

### Release Notes

<details>
<summary>googleapis/python-dataproc</summary>

### [`v0.8.1`](https://github.com/googleapis/python-dataproc/blob/master/CHANGELOG.md#&#8203;081-httpswwwgithubcomgoogleapispython-dataproccomparev080v081-2020-06-05)

[Compare Source](https://github.com/googleapis/python-dataproc/compare/v0.8.0...v0.8.1)

</details>

---

### Renovate configuration

:date: **Schedule**: At any time (no schedule defined).

:vertical_traffic_light: **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

:recycle: **Rebasing**: Never, or you tick the rebase/retry checkbox.

:no_bell: **Ignore**: Close this PR and you won't be reminded about this update again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

---

This PR has been generated by [WhiteSource Renovate](https://renovate.whitesourcesoftware.com). View repository job log [here](https://app.renovatebot.com/dashboard#GoogleCloudPlatform/python-docs-samples).

Author: renovate-bot

dataproc/requirements.txt

@@ -3,4 +3,4 @@ google-auth==1.16.1
 google-auth-httplib2==0.0.3
 google-cloud==0.34.0
 google-cloud-storage==1.28.1
-google-cloud-dataproc==0.8.0
+google-cloud-dataproc==0.8.1