deps: update dependency com.google.cloud:google-cloud-datastore-bom to v2.9.0 (#4517)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:google-cloud-datastore-bom](https://togithub.com/googleapis/java-datastore) | `2.8.0` -> `2.9.0` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-datastore-bom/2.9.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-datastore-bom/2.9.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-datastore-bom/2.9.0/compatibility-slim/2.8.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-datastore-bom/2.9.0/confidence-slim/2.8.0)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

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

### [`v2.9.0`](https://togithub.com/googleapis/java-datastore/blob/HEAD/CHANGELOG.md#&#8203;290-httpsgithubcomgoogleapisjava-datastorecomparev280v290-2022-06-22)

[Compare Source](https://togithub.com/googleapis/java-datastore/compare/v2.8.0...v2.9.0)

##### Features

-   support readTime in Datastore query splitter. ([#&#8203;763](https://togithub.com/googleapis/java-datastore/issues/763)) ([61758e0](https://togithub.com/googleapis/java-datastore/commit/61758e02c30c8410dd397d0cc77c987332c4f11c))

##### Documentation

-   **sample:** clean up README for native image sample ([#&#8203;771](https://togithub.com/googleapis/java-datastore/issues/771)) ([7358aa3](https://togithub.com/googleapis/java-datastore/commit/7358aa34ec9d3d52aae3195fea718ef748ab22b1))

##### Dependencies

-   update dependency org.graalvm.buildtools:junit-platform-native to v0.9.12 ([#&#8203;773](https://togithub.com/googleapis/java-datastore/issues/773)) ([cab7e54](https://togithub.com/googleapis/java-datastore/commit/cab7e54359a4fad5fca23b89a9cf52f95e53e19e))
-   update dependency org.graalvm.buildtools:native-maven-plugin to v0.9.12 ([#&#8203;774](https://togithub.com/googleapis/java-datastore/issues/774)) ([496c1bc](https://togithub.com/googleapis/java-datastore/commit/496c1bcb4c7343fd8330629f82ca9f96fb1a9acc))

</details>

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Author: renovate-bot

google-cloud-bom/pom.xml

@@ -352,7 +352,7 @@
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>google-cloud-datastore-bom</artifactId>
-        <version>2.8.0</version>
+        <version>2.9.0</version>
         <type>pom</type>
         <scope>import</scope>
       </dependency>