chore(deps): update dependency google-cloud-bigquery to v1.27.2 (#74)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [google-cloud-bigquery](https://github.com/googleapis/python-bigquery) | minor | `==1.26.1` -> `==1.27.2` |

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### Release Notes

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

### [`v1.27.2`](https://github.com/googleapis/python-bigquery/blob/master/CHANGELOG.md#&#8203;1272-httpswwwgithubcomgoogleapispython-bigquerycomparev1271v1272-2020-08-18)

[Compare Source](https://github.com/googleapis/python-bigquery/compare/v1.26.1...v1.27.2)

</details>

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samples/snippets/requirements.txt

@@ -2,4 +2,4 @@ google-cloud-storage==1.30.0
 google-cloud-asset==2.0.0
 google-cloud-resource-manager==0.30.2
 google-cloud-pubsub==1.7.0
-google-cloud-bigquery==1.26.1
+google-cloud-bigquery==1.27.2