chore(deps): update dependency google-cloud-scheduler to v2 (#32)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [google-cloud-scheduler](https://togithub.com/googleapis/python-scheduler) | major | `==1.3.0` -> `==2.0.0` |

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### Release Notes

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

### [`v2.0.0`](https://togithub.com/googleapis/python-scheduler/blob/master/CHANGELOG.md#&#8203;200-httpswwwgithubcomgoogleapispython-schedulercomparev130v200-2020-08-27)

[Compare Source](https://togithub.com/googleapis/python-scheduler/compare/v1.3.0...v2.0.0)

##### ⚠ BREAKING CHANGES

-   migrate to microgenerator ([#&#8203;29](https://togithub.com/googleapis/python-scheduler/issues/29))

##### Features

-   migrate to microgenerator ([#&#8203;29](https://www.github.com/googleapis/python-scheduler/issues/29)) ([82f66ed](https://www.github.com/googleapis/python-scheduler/commit/82f66ed9c163b2f6597bf5661469ca9ca1bef741))

##### Bug Fixes

-   update retry configs ([#&#8203;20](https://www.github.com/googleapis/python-scheduler/issues/20)) ([7f82c9f](https://www.github.com/googleapis/python-scheduler/commit/7f82c9ffc292d72907de66bf6d5fa39e38d26085))

</details>

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scheduler/snippets/requirements.txt

@@ -1,3 +1,3 @@
 Flask==1.1.2
 gunicorn==20.0.4
-google-cloud-scheduler==1.3.0
+google-cloud-scheduler==2.0.0