deps: update dependency com.google.cloud:google-cloud-bigquerydatatransfer-bom to v2.2.6 (#4519)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:google-cloud-bigquerydatatransfer-bom](https://togithub.com/googleapis/java-bigquerydatatransfer) | `2.2.5` -> `2.2.6` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-bigquerydatatransfer-bom/2.2.6/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-bigquerydatatransfer-bom/2.2.6/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-bigquerydatatransfer-bom/2.2.6/compatibility-slim/2.2.5)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-bigquerydatatransfer-bom/2.2.6/confidence-slim/2.2.5)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

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

### [`v2.2.6`](https://togithub.com/googleapis/java-bigquerydatatransfer/blob/HEAD/CHANGELOG.md#&#8203;226-httpsgithubcomgoogleapisjava-bigquerydatatransfercomparev225v226-2022-06-22)

[Compare Source](https://togithub.com/googleapis/java-bigquerydatatransfer/compare/v2.2.5...v2.2.6)

##### Dependencies

-   update dependency com.google.cloud:google-cloud-bigquery to v2.13.4 ([#&#8203;1398](https://togithub.com/googleapis/java-bigquerydatatransfer/issues/1398)) ([5debd3d](https://togithub.com/googleapis/java-bigquerydatatransfer/commit/5debd3d2d4679f939bdfecb8a7bf721d1c14589d))

</details>

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Author: renovate-bot

google-cloud-bom/pom.xml

@@ -226,7 +226,7 @@
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>google-cloud-bigquerydatatransfer-bom</artifactId>
-        <version>2.2.5</version>
+        <version>2.2.6</version>
         <type>pom</type>
         <scope>import</scope>
       </dependency>