Upgrade to Spring Framework 5.0.8

Closes gh-13704

Author: snicoll

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

@@ -151,7 +151,7 @@
 		<slf4j.version>1.7.25</slf4j.version>
 		<snakeyaml.version>1.19</snakeyaml.version>
 		<solr.version>6.6.5</solr.version>
-		<spring.version>5.0.8.BUILD-SNAPSHOT</spring.version>
+		<spring.version>5.0.8.RELEASE</spring.version>
 		<spring-amqp.version>2.0.5.BUILD-SNAPSHOT</spring-amqp.version>
 		<spring-batch.version>4.0.1.RELEASE</spring-batch.version>
 		<spring-cloud-connectors.version>2.0.2.RELEASE</spring-cloud-connectors.version>