Upgrade the version of google/errorprone plug-in

This CL upgraded google/errorprone plug-in to 2.3.3 and resolved
some warnings detected from the plug-in.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=238047862

java/google/registry/model/common/EntityGroupRoot.java

@@ -36,6 +36,7 @@ import google.registry.model.BackupGroupRoot;
 @Entity
 public class EntityGroupRoot extends BackupGroupRoot {
 
+  @SuppressWarnings("unused")
   @Id
   private String id;