Upgrade to Gson 2.8.6

Closes gh-18779

Author: snicoll

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

@@ -66,7 +66,7 @@
 		<glassfish-el.version>3.0.0</glassfish-el.version>
 		<glassfish-jaxb.version>2.3.1</glassfish-jaxb.version>
 		<groovy.version>2.5.8</groovy.version>
-		<gson.version>2.8.5</gson.version>
+		<gson.version>2.8.6</gson.version>
 		<h2.version>1.4.200</h2.version>
 		<hamcrest.version>1.3</hamcrest.version>
 		<hazelcast.version>3.11.4</hazelcast.version>