Start building against Spring Data Kay SR5 snapshots

See gh-12234

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

@@ -145,7 +145,7 @@
 		<spring-amqp.version>2.0.2.RELEASE</spring-amqp.version>
 		<spring-batch.version>4.0.0.RELEASE</spring-batch.version>
 		<spring-cloud-connectors.version>2.0.1.RELEASE</spring-cloud-connectors.version>
-		<spring-data-releasetrain.version>Kay-SR4</spring-data-releasetrain.version>
+		<spring-data-releasetrain.version>Kay-BUILD-SNAPSHOT</spring-data-releasetrain.version>
 		<spring-hateoas.version>0.24.0.RELEASE</spring-hateoas.version>
 		<spring-integration.version>5.0.3.BUILD-SNAPSHOT</spring-integration.version>
 		<spring-kafka.version>2.1.2.RELEASE</spring-kafka.version>