chore(deps): update dependency google-cloud-bigquery to v2.20.0 (#154)

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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) | `==2.16.0` -> `==2.20.0` | [![age](https://badges.renovateapi.com/packages/pypi/google-cloud-bigquery/2.20.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/pypi/google-cloud-bigquery/2.20.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/pypi/google-cloud-bigquery/2.20.0/compatibility-slim/2.16.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/pypi/google-cloud-bigquery/2.20.0/confidence-slim/2.16.0)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

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

### [`v2.20.0`](https://togithub.com/googleapis/python-bigquery/blob/master/CHANGELOG.md#&#8203;2200-httpswwwgithubcomgoogleapispython-bigquerycomparev2190v2200-2021-06-07)

[Compare Source](https://togithub.com/googleapis/python-bigquery/compare/v2.19.0...v2.20.0)

##### Features

-   support script options in query job config ([#&#8203;690](https://www.github.com/googleapis/python-bigquery/issues/690)) ([1259e16](https://www.github.com/googleapis/python-bigquery/commit/1259e16394784315368e8be959c1ac097782b62e))

### [`v2.19.0`](https://togithub.com/googleapis/python-bigquery/blob/master/CHANGELOG.md#&#8203;2190-httpswwwgithubcomgoogleapispython-bigquerycomparev2180v2190-2021-06-06)

[Compare Source](https://togithub.com/googleapis/python-bigquery/compare/v2.18.0...v2.19.0)

##### Features

-   list_tables, list_projects, list_datasets, list_models, list_routines, and list_jobs now accept a page_size parameter to control page size  ([#&#8203;686](https://www.github.com/googleapis/python-bigquery/issues/686)) ([1f1c4b7](https://www.github.com/googleapis/python-bigquery/commit/1f1c4b7ba4390fc4c5c8186bc22b83b45304ca06))

### [`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))

### [`v2.17.0`](https://togithub.com/googleapis/python-bigquery/blob/master/CHANGELOG.md#&#8203;2170-httpswwwgithubcomgoogleapispython-bigquerycomparev2161v2170-2021-05-21)

[Compare Source](https://togithub.com/googleapis/python-bigquery/compare/v2.16.1...v2.17.0)

##### Features

-   detect obsolete BQ Storage extra at runtime ([#&#8203;666](https://www.github.com/googleapis/python-bigquery/issues/666)) ([bd7dbda](https://www.github.com/googleapis/python-bigquery/commit/bd7dbdae5c972b16bafc53c67911eeaa3255a880))
-   Support parameterized NUMERIC, BIGNUMERIC, STRING, and BYTES types ([#&#8203;673](https://www.github.com/googleapis/python-bigquery/issues/673)) ([45421e7](https://www.github.com/googleapis/python-bigquery/commit/45421e73bfcddb244822e6a5cd43be6bd1ca2256))

##### Bug Fixes

-   **tests:** invalid path to strptime() ([#&#8203;672](https://www.github.com/googleapis/python-bigquery/issues/672)) ([591cdd8](https://www.github.com/googleapis/python-bigquery/commit/591cdd851bb1321b048a05a378a0ef48d3ade462))

##### [2.16.1](https://www.github.com/googleapis/python-bigquery/compare/v2.16.0...v2.16.1) (2021-05-12)

##### Bug Fixes

-   executemany rowcount only reflected the last execution ([#&#8203;660](https://www.github.com/googleapis/python-bigquery/issues/660)) ([aeadc8c](https://www.github.com/googleapis/python-bigquery/commit/aeadc8c2d614bb9f0883ec901fca48930f3aaf19))

### [`v2.16.1`](https://togithub.com/googleapis/python-bigquery/blob/master/CHANGELOG.md#&#8203;2161-httpswwwgithubcomgoogleapispython-bigquerycomparev2160v2161-2021-05-12)

[Compare Source](https://togithub.com/googleapis/python-bigquery/compare/v2.16.0...v2.16.1)

</details>

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bigquery-datatransfer/snippets/requirements-test.txt

@@ -1,3 +1,3 @@
-google-cloud-bigquery==2.16.0
+google-cloud-bigquery==2.20.0
 pytest==6.2.4
 mock==4.0.3