deps: update dependency com.google.cloud:google-cloud-pubsub-bom to v1.123.4 (#5840)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:google-cloud-pubsub-bom](https://togithub.com/googleapis/java-pubsub) | `1.123.3` -> `1.123.4` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-pubsub-bom/1.123.4/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-pubsub-bom/1.123.4/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-pubsub-bom/1.123.4/compatibility-slim/1.123.3)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-pubsub-bom/1.123.4/confidence-slim/1.123.3)](https://docs.renovatebot.com/merge-confidence/) |

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### ⚠ Dependency Lookup Warnings ⚠

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### Release Notes

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

### [`v1.123.4`](https://togithub.com/googleapis/java-pubsub/blob/HEAD/CHANGELOG.md#&#8203;11234-httpsgithubcomgoogleapisjava-pubsubcomparev11233v11234-2023-02-22)

[Compare Source](https://togithub.com/googleapis/java-pubsub/compare/v1.123.3...v1.123.4)

##### Dependencies

-   Update dependency com.google.cloud:google-cloud-bigquery to v2.23.0 ([#&#8203;1496](https://togithub.com/googleapis/java-pubsub/issues/1496)) ([713d727](https://togithub.com/googleapis/java-pubsub/commit/713d727db447f02e3c6cc7dfbb656fcebba54121))

</details>

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Author: renovate-bot

google-cloud-bom/pom.xml

@@ -224,7 +224,7 @@
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>google-cloud-pubsub-bom</artifactId>
-        <version>1.123.3</version>
+        <version>1.123.4</version>
         <type>pom</type>
         <scope>import</scope>
       </dependency>