[Java] Upgrade to Mockito 3.6.28.

Author: mjpt777

build.gradle

@@ -49,7 +49,7 @@ def javaLauncher = javaToolchains.launcherFor {
 
 def checkstyleVersion = '8.37'
 def hamcrestVersion = '2.2'
-def mockitoVersion = '3.6.0'
+def mockitoVersion = '3.6.28'
 def junitVersion = '5.7.0'
 def jmhVersion = '1.26'
 def agronaVersion = '1.8.0'