chore(deps): bump com.google.cloud:libraries-bom in /pubsub (#630)

Bumps [com.google.cloud:libraries-bom](https://github.com/googleapis/java-cloud-bom) from 26.25.0 to 26.26.0.
- [Release notes](https://github.com/googleapis/java-cloud-bom/releases)
- [Changelog](https://github.com/googleapis/java-cloud-bom/blob/main/release-please-config.json)
- [Commits](googleapis/java-cloud-bom@v26.25.0...v26.26.0)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

pubsub/build.gradle.kts

@@ -11,7 +11,7 @@ repositories {
 }
 
 dependencies {
-    implementation(platform("com.google.cloud:libraries-bom:26.25.0"))
+    implementation(platform("com.google.cloud:libraries-bom:26.26.0"))
     implementation("com.google.cloud:google-cloud-core")
     implementation("com.google.cloud:google-cloud-pubsub")
     implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.3")