Updated ErrorProne version

Updated ErrorProne version and removed suppression due to buggy UnusedVariable rule implementation

Author: jimbethancourt

change-proneness-ranker/src/main/java/org/hjug/git/GitLogReader.java

@@ -15,7 +15,6 @@
 import java.io.*;
 import java.util.*;
 
-@SuppressWarnings("UnusedVariable") //suppressing due to Errorprone issue in version 2.4.0
 @Slf4j
 public class GitLogReader implements RepositoryLogReader {
 

pom.xml

@@ -59,7 +59,7 @@
         <javac.version>9+181-r4173-1</javac.version>
 
         <!--Compiler plugins-->
-        <errorprone.version>2.4.0</errorprone.version>
+        <errorprone.version>2.5.1</errorprone.version>
         <lombok.version>1.18.12</lombok.version>
 
         <spotbugs.maven.plugin.version>4.0.0</spotbugs.maven.plugin.version>