Update error-prone to 2.4.0

Author: nicerloop

plexus-compilers/plexus-compiler-javac-errorprone/pom.xml

@@ -29,7 +29,7 @@
     <dependency>
       <groupId>com.google.errorprone</groupId>
       <artifactId>error_prone_core</artifactId>
-      <version>2.3.4</version>
+      <version>2.4.0</version>
     </dependency>
   </dependencies>