chore(deps): update dependency @google-cloud/datastore to v8 (#1518)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [@google-cloud/datastore](https://togithub.com/googleapis/nodejs-datastore) | [`^7.0.0` -> `^8.0.0`](https://renovatebot.com/diffs/npm/@google-cloud%2fdatastore/7.5.1/8.0.0) | [![age](https://developer.mend.io/api/mc/badges/age/npm/@google-cloud%2fdatastore/8.0.0?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://developer.mend.io/api/mc/badges/adoption/npm/@google-cloud%2fdatastore/8.0.0?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://developer.mend.io/api/mc/badges/compatibility/npm/@google-cloud%2fdatastore/7.5.1/8.0.0?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://developer.mend.io/api/mc/badges/confidence/npm/@google-cloud%2fdatastore/7.5.1/8.0.0?slim=true)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

<details>
<summary>googleapis/nodejs-datastore (@&#8203;google-cloud/datastore)</summary>

### [`v8.0.0`](https://togithub.com/googleapis/nodejs-datastore/blob/HEAD/CHANGELOG.md#800-2023-08-09)

[Compare Source](https://togithub.com/googleapis/nodejs-datastore/compare/v7.5.1...v8.0.0)

##### ⚠ BREAKING CHANGES

-   upgrade to Node 14

##### Miscellaneous Chores

-   Upgrade to Node 14 ([b7904f1](https://togithub.com/googleapis/nodejs-datastore/commit/b7904f12b1d398a5b0e6fefc2a002c404f9e7d3d))

</details>

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package.json

@@ -49,7 +49,7 @@
   },
   "devDependencies": {
     "@compodoc/compodoc": "1.1.19",
-    "@google-cloud/datastore": "^7.0.0",
+    "@google-cloud/datastore": "^8.0.0",
     "@grpc/proto-loader": "^0.7.0",
     "@types/builtin-modules": "^2.0.0",
     "@types/console-log-level": "^1.4.0",