deps: update dependency com.google.cloud:google-cloud-firestore-bom to v3.31.6 (#7056)

This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:google-cloud-firestore-bom](https://redirect.github.com/googleapis/java-firestore) | `3.31.4` -> `3.31.6` | [![age](https://developer.mend.io/api/mc/badges/age/maven/com.google.cloud:google-cloud-firestore-bom/3.31.6?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://developer.mend.io/api/mc/badges/adoption/maven/com.google.cloud:google-cloud-firestore-bom/3.31.6?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://developer.mend.io/api/mc/badges/compatibility/maven/com.google.cloud:google-cloud-firestore-bom/3.31.4/3.31.6?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://developer.mend.io/api/mc/badges/confidence/maven/com.google.cloud:google-cloud-firestore-bom/3.31.4/3.31.6?slim=true)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

<details>
<summary>googleapis/java-firestore (com.google.cloud:google-cloud-firestore-bom)</summary>

### [`v3.31.6`](https://redirect.github.com/googleapis/java-firestore/blob/HEAD/CHANGELOG.md#3316-2025-06-04)

[Compare Source](https://redirect.github.com/googleapis/java-firestore/compare/v3.31.5...v3.31.6)

##### Bug Fixes

-   **deps:** Update the Java code generator (gapic-generator-java) to 2.59.0 ([f44e1e5](https://redirect.github.com/googleapis/java-firestore/commit/f44e1e5be5288d1af95cf9deaacf327a64bf9178))

##### Dependencies

-   Update dependency com.google.cloud:sdk-platform-java-config to v3.49.0 ([#&#8203;2135](https://redirect.github.com/googleapis/java-firestore/issues/2135)) ([4006eaf](https://redirect.github.com/googleapis/java-firestore/commit/4006eaf7a3758b277636d8a31233770f8354eb6e))
-   Update googleapis/sdk-platform-java action to v2.59.0 ([#&#8203;2133](https://redirect.github.com/googleapis/java-firestore/issues/2133)) ([b1b78bb](https://redirect.github.com/googleapis/java-firestore/commit/b1b78bbfbee15f094c2bf4818babe1e1d556cd18))

### [`v3.31.5`](https://redirect.github.com/googleapis/java-firestore/blob/HEAD/CHANGELOG.md#3315-2025-05-28)

[Compare Source](https://redirect.github.com/googleapis/java-firestore/compare/v3.31.4...v3.31.5)

##### Bug Fixes

-   **deps:** Update the Java code generator (gapic-generator-java) to 2.58.0 ([819dc99](https://redirect.github.com/googleapis/java-firestore/commit/819dc99ea4f90a8b5cba21cc7016921aa156f3da))

##### Dependencies

-   Update dependency com.diffplug.spotless:spotless-maven-plugin to v2.44.5 ([#&#8203;2128](https://redirect.github.com/googleapis/java-firestore/issues/2128)) ([b100ac3](https://redirect.github.com/googleapis/java-firestore/commit/b100ac3d75e8967e18589d5d719e5bf63969c438))
-   Update dependency com.google.api.grpc:proto-google-cloud-trace-v1 to v2.63.0 ([#&#8203;2122](https://redirect.github.com/googleapis/java-firestore/issues/2122)) ([d5f6a8e](https://redirect.github.com/googleapis/java-firestore/commit/d5f6a8ea2e463143fb0fe4328de87a9886f1e78c))
-   Update dependency com.google.cloud:google-cloud-trace to v2.63.0 ([#&#8203;2123](https://redirect.github.com/googleapis/java-firestore/issues/2123)) ([504fdb4](https://redirect.github.com/googleapis/java-firestore/commit/504fdb464783af39b8844392f84bcf8800dd0862))
-   Update dependency com.google.cloud.opentelemetry:exporter-trace to v0.35.0 ([#&#8203;2129](https://redirect.github.com/googleapis/java-firestore/issues/2129)) ([f5013ad](https://redirect.github.com/googleapis/java-firestore/commit/f5013add2338af8b5780df65c691999123795a37))

</details>

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Author: renovate-bot

google-cloud-bom/pom.xml

@@ -200,7 +200,7 @@
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>google-cloud-firestore-bom</artifactId>
-        <version>3.31.4</version>
+        <version>3.31.6</version>
         <type>pom</type>
         <scope>import</scope>
       </dependency>