Upgrade Mockito to 5.21.0

Author: wojciech-adaptive

gradle/libs.versions.toml

@@ -10,7 +10,7 @@ httpcore = "4.4.14"
 jmh = "1.37"
 json = "20250517"
 junit = "6.0.1"
-mockito = "5.20.0"
+mockito = "5.21.0"
 plexus = "3.3.0"
 sbe = "1.36.2"
 shadow = "8.3.9"