chore(deps): update dependency google-cloud-bigquery to v1.26.1 (#62)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [google-cloud-bigquery](https://togithub.com/googleapis/python-bigquery) | minor | `==1.25.0` -> `==1.26.1` |

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### Release Notes

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

### [`v1.26.1`](https://togithub.com/googleapis/python-bigquery/blob/master/CHANGELOG.md#&#8203;1261-httpswwwgithubcomgoogleapispython-bigquerycomparev1260v1261-2020-07-25)

[Compare Source](https://togithub.com/googleapis/python-bigquery/compare/v1.26.0...v1.26.1)

### [`v1.26.0`](https://togithub.com/googleapis/python-bigquery/blob/master/CHANGELOG.md#&#8203;1260-httpswwwgithubcomgoogleapispython-bigquerycomparev1250v1260-2020-07-20)

[Compare Source](https://togithub.com/googleapis/python-bigquery/compare/v1.25.0...v1.26.0)

##### Features

-   use BigQuery Storage client by default (if dependencies available) ([#&#8203;55](https://www.github.com/googleapis/python-bigquery/issues/55)) ([e75ff82](https://www.github.com/googleapis/python-bigquery/commit/e75ff8297c65981545b097f75a17cf9e78ac6772)), closes [#&#8203;91](https://www.github.com/googleapis/python-bigquery/issues/91)
-   **bigquery:** add **eq** method for class PartitionRange and RangePartitioning ([#&#8203;162](https://www.github.com/googleapis/python-bigquery/issues/162)) ([0d2a88d](https://www.github.com/googleapis/python-bigquery/commit/0d2a88d8072154cfc9152afd6d26a60ddcdfbc73))
-   **bigquery:** expose date_as_object parameter to users ([#&#8203;150](https://www.github.com/googleapis/python-bigquery/issues/150)) ([a2d5ce9](https://www.github.com/googleapis/python-bigquery/commit/a2d5ce9e97992318d7dc85c51c053cab74e25a11))
-   **bigquery:** expose date_as_object parameter to users ([#&#8203;150](https://www.github.com/googleapis/python-bigquery/issues/150)) ([cbd831e](https://www.github.com/googleapis/python-bigquery/commit/cbd831e08024a67148723afd49e1db085e0a862c))

##### Bug Fixes

-   dry run queries with DB API cursor ([#&#8203;128](https://www.github.com/googleapis/python-bigquery/issues/128)) ([bc33a67](https://www.github.com/googleapis/python-bigquery/commit/bc33a678a765f0232615aa2038b8cc67c88468a0))
-   omit `NaN` values when uploading from `insert_rows_from_dataframe` ([#&#8203;170](https://www.github.com/googleapis/python-bigquery/issues/170)) ([f9f2f45](https://www.github.com/googleapis/python-bigquery/commit/f9f2f45bc009c03cd257441bd4b6beb1754e2177))

##### Documentation

-   **bigquery:** add client thread-safety documentation ([#&#8203;132](https://www.github.com/googleapis/python-bigquery/issues/132)) ([fce76b3](https://www.github.com/googleapis/python-bigquery/commit/fce76b3776472b1da798df862a3405e659e35bab))
-   **bigquery:** add docstring for conflict exception ([#&#8203;171](https://www.github.com/googleapis/python-bigquery/issues/171)) ([9c3409b](https://www.github.com/googleapis/python-bigquery/commit/9c3409bb06218bf499620544f8e92802df0cce47))
-   **bigquery:** consistent use of optional keyword ([#&#8203;153](https://www.github.com/googleapis/python-bigquery/issues/153)) ([79d8c61](https://www.github.com/googleapis/python-bigquery/commit/79d8c61064cca18b596a24b6f738c7611721dd5c))
-   **bigquery:** fix the broken docs ([#&#8203;139](https://www.github.com/googleapis/python-bigquery/issues/139)) ([3235255](https://www.github.com/googleapis/python-bigquery/commit/3235255cc5f483949f34d2e8ef13b372e8713782))

</details>

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asset/snippets/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==1.25.0
+google-cloud-bigquery==1.26.1