Upgrade to Spring Integration Java DSL 1.2.0.RC1

Closes gh-7000

spring-boot-dependencies/pom.xml

@@ -151,7 +151,7 @@
 		<spring-data-releasetrain.version>Ingalls-M1</spring-data-releasetrain.version>
 		<spring-hateoas.version>0.21.0.RELEASE</spring-hateoas.version>
 		<spring-integration.version>4.3.2.RELEASE</spring-integration.version>
-		<spring-integration-java-dsl.version>1.2.0.BUILD-SNAPSHOT</spring-integration-java-dsl.version>
+		<spring-integration-java-dsl.version>1.2.0.RC1</spring-integration-java-dsl.version>
 		<spring-loaded.version>1.2.6.RELEASE</spring-loaded.version>
 		<spring-mobile.version>1.1.5.RELEASE</spring-mobile.version>
 		<spring-plugin.version>1.2.0.RELEASE</spring-plugin.version>