MINOR: Bump org.mockito:mockito-bom from 5.17.0 to 5.21.0

Bumps [org.mockito:mockito-bom](https://github.com/mockito/mockito) from 5.17.0 to 5.21.0.
- [Release notes](https://github.com/mockito/mockito/releases)
- [Commits](mockito/mockito@v5.17.0...v5.21.0)

---
updated-dependencies:
- dependency-name: org.mockito:mockito-bom
  dependency-version: 5.21.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

pom.xml

@@ -104,7 +104,7 @@ under the License.
     <dep.hadoop.version>3.4.2</dep.hadoop.version>
     <dep.fbs.version>25.2.10</dep.fbs.version>
     <dep.avro.version>1.12.1</dep.avro.version>
-    <dep.mockito-bom.version>5.17.0</dep.mockito-bom.version>
+    <dep.mockito-bom.version>5.21.0</dep.mockito-bom.version>
     <arrow.vector.classifier></arrow.vector.classifier>
     <forkCount>2</forkCount>
     <checkstyle.version>10.23.0</checkstyle.version>