[Java] Upgrade to JUnit 6.0.3.

Author: vyazelenko

gradle/libs.versions.toml

@@ -8,7 +8,7 @@ httpcore = "4.4.14"
 jqwik = "1.9.3"
 jmh = "1.37"
 json = "20251224"
-junit = "6.0.2"
+junit = "6.0.3"
 mockito = "5.21.0"
 plexus = "3.3.0"
 shadow = "9.3.1"