Upgrade to Groovy 2.5.7

Closes gh-16845

Author: snicoll

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

@@ -63,7 +63,7 @@
 		<elasticsearch.version>6.7.2</elasticsearch.version>
 		<glassfish-el.version>3.0.2</glassfish-el.version>
 		<glassfish-jaxb.version>2.3.2</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>