chore(deps): update dependency google-cloud-bigquery to v2.18.0 (#198)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [google-cloud-bigquery](https://togithub.com/googleapis/python-bigquery) | `==2.17.0` -> `==2.18.0` | [![age](https://badges.renovateapi.com/packages/pypi/google-cloud-bigquery/2.18.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/pypi/google-cloud-bigquery/2.18.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/pypi/google-cloud-bigquery/2.18.0/compatibility-slim/2.17.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/pypi/google-cloud-bigquery/2.18.0/confidence-slim/2.17.0)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

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

### [`v2.18.0`](https://togithub.com/googleapis/python-bigquery/blob/master/CHANGELOG.md#&#8203;2180-httpswwwgithubcomgoogleapispython-bigquerycomparev2170v2180-2021-06-02)

[Compare Source](https://togithub.com/googleapis/python-bigquery/compare/v2.17.0...v2.18.0)

##### Features

-   add support for Parquet options ([#&#8203;679](https://www.github.com/googleapis/python-bigquery/issues/679)) ([d792ce0](https://www.github.com/googleapis/python-bigquery/commit/d792ce09388a6ee3706777915dd2818d4c854f79))

</details>

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asset/snippets/snippets/requirements.txt

@@ -2,4 +2,4 @@ google-cloud-storage==1.38.0
 google-cloud-asset==2.2.0
 google-cloud-resource-manager==0.30.3
 google-cloud-pubsub==2.5.0
-google-cloud-bigquery==2.17.0
+google-cloud-bigquery==2.18.0