Upgrade Log4j to 2.16.0 (Tests Only)

Author: garyrussell

build.gradle

@@ -60,7 +60,7 @@ ext {
 	junit4Version = '4.13.2'
 	junitJupiterVersion = '5.8.1'
 	kafkaVersion = '3.0.0'
-	log4jVersion = '2.15.0'
+	log4jVersion = '2.16.0'
 	micrometerVersion = '1.8.0'
 	mockitoVersion = '4.0.0'
 	reactorVersion = '2020.0.13'