Bump libraries-bom from 26.3.0 to 26.4.0

Bumps [libraries-bom](https://github.com/googleapis/java-cloud-bom) from 26.3.0 to 26.4.0.
- [Release notes](https://github.com/googleapis/java-cloud-bom/releases)
- [Changelog](https://github.com/googleapis/java-cloud-bom/blob/main/CHANGELOG.md)
- [Commits](googleapis/java-cloud-bom@libraries-bom-v26.3.0...libraries-bom-v26.4.0)

---
updated-dependencies:
- dependency-name: com.google.cloud:libraries-bom
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

pom.xml

@@ -57,7 +57,7 @@
             <dependency>
                 <groupId>com.google.cloud</groupId>
                 <artifactId>libraries-bom</artifactId>
-                <version>26.3.0</version>
+                <version>26.4.0</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>