Upgrade to Groovy 2.5.7

Closes gh-16840

Author: snicoll

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

@@ -64,7 +64,7 @@
 		<elasticsearch.version>6.4.3</elasticsearch.version>
 		<glassfish-el.version>3.0.0</glassfish-el.version>
 		<glassfish-jaxb.version>2.3.1</glassfish-jaxb.version>
-		<groovy.version>2.5.6</groovy.version>
+		<groovy.version>2.5.7</groovy.version>
 		<gson.version>2.8.5</gson.version>
 		<h2.version>1.4.199</h2.version>
 		<hamcrest.version>1.3</hamcrest.version>