Upgrade to Caffeine 2.5.6

Closes gh-10398

Author: wilkinsona

spring-boot-dependencies/pom.xml

@@ -55,7 +55,7 @@
 		<atomikos.version>4.0.4</atomikos.version>
 		<bitronix.version>2.1.4</bitronix.version>
 		<byte-buddy.version>1.7.5</byte-buddy.version>
-		<caffeine.version>2.5.5</caffeine.version>
+		<caffeine.version>2.5.6</caffeine.version>
 		<cassandra-driver.version>3.3.0</cassandra-driver.version>
 		<classmate.version>1.3.4</classmate.version>
 		<commons-beanutils.version>1.9.3</commons-beanutils.version>