[Java] Bump Mockito to 5.16.0.

Author: vyazelenko

gradle/libs.versions.toml

@@ -10,7 +10,7 @@ jqwik = "1.9.2"
 jmh = "1.37"
 json = "20250107"
 junit = "5.12.0"
-mockito = "5.15.2"
+mockito = "5.16.0"
 plexus = "3.3.0"
 shadow = "8.3.6"
 versions = "0.52.0"