Bump org.mockito:mockito-bom from 5.16.1 to 5.21.0

Bumps [org.mockito:mockito-bom](https://github.com/mockito/mockito) from 5.16.1 to 5.21.0.
- [Release notes](https://github.com/mockito/mockito/releases)
- [Commits](mockito/mockito@v5.16.1...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]

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 jakarta-websocket = "2.2.0"
 org-apache-derby = "10.16.1.1"
-org-mockito = "5.16.1"
+org-mockito = "5.21.0"
 org-springframework-boot = "4.0.1-SNAPSHOT"
 
 [libraries]