Upgrade to Jackson 2.8.4

Closes gh-7282

spring-boot-dependencies/pom.xml

@@ -93,7 +93,7 @@
 		<httpclient.version>4.5.2</httpclient.version>
 		<httpcore.version>4.4.5</httpcore.version>
 		<infinispan.version>8.2.4.Final</infinispan.version>
-		<jackson.version>2.8.3</jackson.version>
+		<jackson.version>2.8.4</jackson.version>
 		<janino.version>2.7.8</janino.version>
 		<javassist.version>3.20.0-GA</javassist.version> <!-- Same as Hibernate -->
 		<javax-cache.version>1.0.0</javax-cache.version>