[Java] Upgrade to Mockito 3.4.4.

Author: mjpt777

build.gradle

@@ -30,7 +30,7 @@ defaultTasks 'clean', 'build'
 
 def checkstyleVersion = '8.34'
 def hamcrestVersion = '2.2'
-def mockitoVersion = '3.4.3'
+def mockitoVersion = '3.4.4'
 def junitVersion = '5.6.2'
 def jmhVersion = '1.23'
 def agronaVersion = '1.6.0'