Update dependency org.junit.jupiter:junit-jupiter to v6

Author: renovate[bot]

gradle/libs.versions.toml

@@ -2,7 +2,7 @@
 dkimcore = "1.6.1"
 dkim-gradle = "1.4.7"
 dokkatoo = "2.4.0"
-junit = "5.14.0"
+junit = "6.0.0"
 kotlin = "2.2.21"
 licenser = "0.6.1"
 mockito-kotlin = "6.1.0"