Upgrade to Spring Kafka 2.1.0.RC1

Closes gh-10975

Author: wilkinsona

spring-boot-project/spring-boot-dependencies/pom.xml

@@ -147,7 +147,7 @@
 		<spring-data-releasetrain.version>Kay-SR1</spring-data-releasetrain.version>
 		<spring-hateoas.version>0.24.0.RELEASE</spring-hateoas.version>
 		<spring-integration.version>5.0.0.RC1</spring-integration.version>
-		<spring-kafka.version>2.0.0.RELEASE</spring-kafka.version>
+		<spring-kafka.version>2.1.0.RC1</spring-kafka.version>
 		<spring-ldap.version>2.3.2.RELEASE</spring-ldap.version>
 		<spring-plugin.version>1.2.0.RELEASE</spring-plugin.version>
 		<spring-restdocs.version>2.0.0.RC1</spring-restdocs.version>