Bump org.junit:junit-bom from 5.13.4 to 6.0.0

Bumps [org.junit:junit-bom](https://github.com/junit-team/junit-framework) from 5.13.4 to 6.0.0.
- [Release notes](https://github.com/junit-team/junit-framework/releases)
- [Commits](junit-team/junit-framework@r5.13.4...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]

gradle/libs.versions.toml

@@ -4,7 +4,7 @@ embulk-util-rubytime = "0.4.0"
 
 joda-time = "2.14.0"
 
-junit5 = "5.13.4"
+junit5 = "6.0.0"
 
 checkstyle = "9.3"