Upgrade to Spring Framework 5.1.0.RC1

Closes gh-13911

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

@@ -152,7 +152,7 @@
 		<slf4j.version>1.7.25</slf4j.version>
 		<snakeyaml.version>1.21</snakeyaml.version>
 		<solr.version>7.4.0</solr.version>
-		<spring.version>5.1.0.BUILD-SNAPSHOT</spring.version>
+		<spring.version>5.1.0.RC1</spring.version>
 		<spring-amqp.version>2.1.0.BUILD-SNAPSHOT</spring-amqp.version>
 		<spring-batch.version>4.1.0.M2</spring-batch.version>
 		<spring-cloud-connectors.version>2.0.2.RELEASE</spring-cloud-connectors.version>