deps: update dependency com.google.errorprone:error_prone_annotations to v2.4.0 (#186)

Author: renovate-bot

pom.xml

@@ -162,7 +162,7 @@
     <threeten.version>1.4.4</threeten.version>
     <javax.annotations.version>1.3.2</javax.annotations.version>
     <animal-sniffer.version>1.18</animal-sniffer.version>
-    <errorprone.version>2.3.4</errorprone.version>
+    <errorprone.version>2.4.0</errorprone.version>
   </properties>
 
   <dependencyManagement>