Upgrade Kafka clients to 2.3.1

Author: garyrussell

build.gradle

@@ -58,7 +58,7 @@ ext {
 	jaywayJsonPathVersion = '2.4.0'
 	junit4Version = '4.12'
 	junitJupiterVersion = '5.5.2'
-	kafkaVersion = '2.3.0'
+	kafkaVersion = '2.3.1'
 	log4jVersion = '2.12.1'
 	micrometerVersion = '1.3.0'
 	mockitoVersion = '3.0.0'