[Java] Upgrade to Checkstyle 8.23.

Author: mjpt777

build.gradle

@@ -135,7 +135,7 @@ subprojects {
     jar.enabled = true
 
     dependencies {
-        checkstyle 'com.puppycrawl.tools:checkstyle:8.22'
+        checkstyle 'com.puppycrawl.tools:checkstyle:8.23'
 
         compile 'org.agrona:agrona:1.0.3'
 
@@ -144,7 +144,7 @@ subprojects {
         testCompile 'junit:junit:4.12'
     }
 
-    checkstyle.toolVersion = '8.22'
+    checkstyle.toolVersion = '8.23'
 
     compileJava {
         sourceCompatibility = sbeJavaVersion