csl: Update Caffeine Cache library to 2.9.3

Problem/Solution

We want to keep our dependencies up to date for the ben-manes Caffeine library.
Let’s update to version 2.9.3.

JIRA Issues: CSL-11548

Differential Revision: https://phabricator.twitter.biz/D815761

CHANGELOG.rst

@@ -7,6 +7,11 @@ Note that ``PHAB_ID=#`` and ``RB_ID=#`` correspond to associated messages in com
 Unreleased
 ----------
 
+Runtime Behavior Changes
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+* util: Bump version of Caffeine to 2.9.3. ``PHAB_ID=D815761``
+
 22.1.0
 ------
 

build.sbt

@@ -22,7 +22,7 @@ val zkDependency = "org.apache.zookeeper" % "zookeeper" % zkVersion excludeAll (
 )
 
 val guavaLib = "com.google.guava" % "guava" % "25.1-jre"
-val caffeineLib = "com.github.ben-manes.caffeine" % "caffeine" % "2.9.2"
+val caffeineLib = "com.github.ben-manes.caffeine" % "caffeine" % "2.9.3"
 val jsr305Lib = "com.google.code.findbugs" % "jsr305" % "2.0.1"
 val scalacheckLib = "org.scalacheck" %% "scalacheck" % "1.15.4" % "test"
 val slf4jApi = "org.slf4j" % "slf4j-api" % slf4jVersion