chore(deps): bump org.junit:junit-bom in /flipt-client-java

Bumps [org.junit:junit-bom](https://github.com/junit-team/junit-framework) from 5.11.4 to 6.0.0.
- [Release notes](https://github.com/junit-team/junit-framework/releases)
- [Commits](junit-team/junit-framework@r5.11.4...r6.0.0)

---
updated-dependencies:
- dependency-name: org.junit:junit-bom
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

flipt-client-java/gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 jackson = "2.20.0"
 jna = "5.18.0"
-junit = "5.11.4"
+junit = "6.0.0"
 lombok = "1.18.42"
 
 [libraries]