Update PMD and Checkstyle versions

theodolite-benchmarks/buildSrc/src/main/groovy/theodolite.java-conventions.gradle

@@ -50,7 +50,7 @@ pmd {
   ruleSets = [] // Gradle requires to clean the rule sets first
   ruleSetFiles = files("$rootProject.projectDir/config/pmd.xml")
   ignoreFailures = false
-  toolVersion = "6.8.0"
+  toolVersion = "6.13.0"
 }
 
 checkstyle {
@@ -58,7 +58,7 @@ checkstyle {
   configFile = file("$rootProject.projectDir/config/checkstyle.xml")
   maxWarnings = 0
   ignoreFailures = false
-  toolVersion = "8.12"
+  toolVersion = "8.19"
 }
 
 spotbugs {

theodolite-benchmarks/flink-commons/src/main/java/theodolite/commons/flink/serialization/StatsSerializer.java

@@ -5,7 +5,6 @@ import com.esotericsoftware.kryo.Serializer;
 import com.esotericsoftware.kryo.io.Input;
 import com.esotericsoftware.kryo.io.Output;
 import com.google.common.math.Stats;
-
 import java.io.Serializable;
 
 /**