chore(deps): update dependency google-cloud-datastore to v2.1.6 (#220)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [google-cloud-datastore](https://togithub.com/googleapis/python-datastore) | `==2.1.5` -> `==2.1.6` | [![age](https://badges.renovateapi.com/packages/pypi/google-cloud-datastore/2.1.6/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/pypi/google-cloud-datastore/2.1.6/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/pypi/google-cloud-datastore/2.1.6/compatibility-slim/2.1.5)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/pypi/google-cloud-datastore/2.1.6/confidence-slim/2.1.5)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

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

### [`v2.1.6`](https://togithub.com/googleapis/python-datastore/blob/master/CHANGELOG.md#&#8203;216-httpswwwgithubcomgoogleapispython-datastorecomparev215v216-2021-07-26)

[Compare Source](https://togithub.com/googleapis/python-datastore/compare/v2.1.5...v2.1.6)

</details>

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dlp/snippets/requirements.txt

@@ -1,5 +1,5 @@
 google-cloud-dlp==3.2.1
 google-cloud-storage==1.41.1
 google-cloud-pubsub==2.6.1
-google-cloud-datastore==2.1.5
+google-cloud-datastore==2.1.6
 google-cloud-bigquery==2.23.0