Revert "Upgrade to Spring Data Hopper-SR9"

This commit reverts 2deab52 as the Couchbase driver must be upgraded from
2.2.x to 2.4.x

See gh-8938

spring-boot-dependencies/pom.xml

@@ -149,7 +149,7 @@
 		<spring-amqp.version>1.6.9.RELEASE</spring-amqp.version>
 		<spring-cloud-connectors.version>1.2.3.RELEASE</spring-cloud-connectors.version>
 		<spring-batch.version>3.0.7.RELEASE</spring-batch.version>
-		<spring-data-releasetrain.version>Hopper-SR9</spring-data-releasetrain.version>
+		<spring-data-releasetrain.version>Hopper-SR8</spring-data-releasetrain.version>
 		<spring-hateoas.version>0.20.0.RELEASE</spring-hateoas.version>
 		<spring-integration.version>4.3.9.RELEASE</spring-integration.version>
 		<spring-integration-java-dsl.version>1.1.4.RELEASE</spring-integration-java-dsl.version>