build(deps): Bump org.mockito:mockito-core in /backend (#461)

Bumps [org.mockito:mockito-core](https://github.com/mockito/mockito) from 5.14.1 to 5.15.2.
- [Release notes](https://github.com/mockito/mockito/releases)
- [Commits](mockito/mockito@v5.14.1...v5.15.2)

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

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

backend/build.gradle

@@ -103,7 +103,7 @@ dependencies {
 	testImplementation slf4jDependency
 
 	// https://mvnrepository.com/artifact/org.mockito/mockito-core
-	testImplementation group: 'org.mockito', name: 'mockito-core', version: '5.14.1'
+	testImplementation group: 'org.mockito', name: 'mockito-core', version: '5.15.2'
 }
 
 // --------------- Version Injection ---------------