Bump org.mockito:mockito-bom from 5.3.1 to 5.4.0

Bumps [org.mockito:mockito-bom](https://github.com/mockito/mockito) from 5.3.1 to 5.4.0.
- [Release notes](https://github.com/mockito/mockito/releases)
- [Commits](mockito/mockito@v5.3.1...v5.4.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

build.gradle

@@ -103,7 +103,7 @@ dependencies {
     testImplementation project.deps.gocdPluginApi
     testImplementation group: 'uk.org.webcompere', name: 'system-stubs-jupiter', version: '2.0.2'
     testImplementation group: 'org.assertj', name: 'assertj-core', version: '3.24.2'
-    testImplementation platform('org.mockito:mockito-bom:5.3.1')
+    testImplementation platform('org.mockito:mockito-bom:5.4.0')
     testImplementation group: 'org.mockito', name: 'mockito-core'
     testImplementation group: 'org.skyscreamer', name: 'jsonassert', version: '1.5.1'
     testImplementation group: 'org.jsoup', name: 'jsoup', version: '1.16.1'