chore(deps): update dependency google-cloud-datastore to v1.15.0 (#42)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [google-cloud-datastore](https://togithub.com/googleapis/python-datastore) | minor | `==1.13.2` -> `==1.15.0` |

---

### Release Notes

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

### [`v1.15.0`](https://togithub.com/googleapis/python-datastore/blob/master/CHANGELOG.md#&#8203;1150-httpswwwgithubcomgoogleapispython-datastorecomparev1140v1150-2020-08-14)

[Compare Source](https://togithub.com/googleapis/python-datastore/compare/v1.14.0...v1.15.0)

##### Features

-   add retry and timeout args to API methods ([#&#8203;67](https://www.github.com/googleapis/python-datastore/issues/67)) ([f3283e1](https://www.github.com/googleapis/python-datastore/commit/f3283e14c34c36c8386e4cb6b43c109d469f118c)), closes [#&#8203;3](https://www.github.com/googleapis/python-datastore/issues/3)
-   supply anonymous credentials under emulator ([#&#8203;71](https://www.github.com/googleapis/python-datastore/issues/71)) ([4db3c40](https://www.github.com/googleapis/python-datastore/commit/4db3c4048e53c220eee0aea2063c05292bbc5334)), closes [#&#8203;70](https://www.github.com/googleapis/python-datastore/issues/70)

##### Bug Fixes

-   smooth over system test bumps ([#&#8203;66](https://www.github.com/googleapis/python-datastore/issues/66)) ([8bb17ea](https://www.github.com/googleapis/python-datastore/commit/8bb17ea30ed94c0a298a54cc75c031b67d0a576a))

##### Documentation

-   add docs for admin client ([#&#8203;63](https://www.github.com/googleapis/python-datastore/issues/63)) ([43ff64a](https://www.github.com/googleapis/python-datastore/commit/43ff64a5889aeac321fbead967ec527ede414fa2)), closes [#&#8203;49](https://www.github.com/googleapis/python-datastore/issues/49)

### [`v1.14.0`](https://togithub.com/googleapis/python-datastore/blob/master/CHANGELOG.md#&#8203;1140-httpswwwgithubcomgoogleapispython-datastorecomparev1132v1140-2020-08-05)

[Compare Source](https://togithub.com/googleapis/python-datastore/compare/v1.13.2...v1.14.0)

##### Features

-   pass 'client_options' to base class ctor ([#&#8203;60](https://www.github.com/googleapis/python-datastore/issues/60)) ([2575697](https://www.github.com/googleapis/python-datastore/commit/2575697380a2e57b210a37033f2558de582ec10e)), closes [#&#8203;50](https://www.github.com/googleapis/python-datastore/issues/50)

##### Documentation

-   correct semantics of 'complete_key' arg to 'Client.reserve_ids' ([#&#8203;36](https://www.github.com/googleapis/python-datastore/issues/36)) ([50ed945](https://www.github.com/googleapis/python-datastore/commit/50ed94503da244434df0be58098a0ccf2da54b16))
-   update docs build (via synth) ([#&#8203;58](https://www.github.com/googleapis/python-datastore/issues/58)) ([5bdacd4](https://www.github.com/googleapis/python-datastore/commit/5bdacd4785f3d433e6e7302fc6839a3c5a3314b4)), closes [#&#8203;700](https://www.github.com/googleapis/python-datastore/issues/700)

##### [1.13.2](https://www.github.com/googleapis/python-datastore/compare/v1.13.1...v1.13.2) (2020-07-17)

##### Bug Fixes

-   modify admin pkg name in gapic ([#&#8203;47](https://www.github.com/googleapis/python-datastore/issues/47)) ([5b5011d](https://www.github.com/googleapis/python-datastore/commit/5b5011daf74133ecdd579bf19bbcf356e6f40dad))

##### [1.13.1](https://www.github.com/googleapis/python-datastore/compare/v1.13.0...v1.13.1) (2020-07-13)

##### Bug Fixes

-   add missing datastore admin client files ([#&#8203;43](https://www.github.com/googleapis/python-datastore/issues/43)) ([0d40f87](https://www.github.com/googleapis/python-datastore/commit/0d40f87eeacd2a256d4b45ccb742599b5df93096))

</details>

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dlp/snippets/requirements.txt

@@ -1,5 +1,5 @@
 google-cloud-dlp==2.0.0
 google-cloud-storage==1.30.0
 google-cloud-pubsub==1.7.0
-google-cloud-datastore==1.13.2
+google-cloud-datastore==1.15.0
 google-cloud-bigquery==1.27.2