Build against Spring Framework 5.2.0 snapshots

See gh-18232

Author: philwebb

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

@@ -188,7 +188,7 @@
 		<spring-batch.version>4.2.0.RC1</spring-batch.version>
 		<spring-cloud-connectors.version>2.0.6.RELEASE</spring-cloud-connectors.version>
 		<spring-data-releasetrain.version>Moore-RC3</spring-data-releasetrain.version>
-		<spring-framework.version>5.2.0.RC2</spring-framework.version>
+		<spring-framework.version>5.2.0.BUILD-SNAPSHOT</spring-framework.version>
 		<spring-hateoas.version>1.0.0.RC2</spring-hateoas.version>
 		<spring-integration.version>5.2.0.RC1</spring-integration.version>
 		<spring-kafka.version>2.3.0.RC1</spring-kafka.version>