DeleteAssignee: Make batchUpdateFactory final

Change-Id: Iecc6ef81bedb3acf471c28db1097b01dc8e52cda
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/change/DeleteAssignee.java b/gerrit-server/src/main/java/com/google/gerrit/server/change/DeleteAssignee.java
index beec6ab..45051e7 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/change/DeleteAssignee.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/change/DeleteAssignee.java
@@ -42,12 +42,11 @@
 import com.google.inject.Singleton;
 
 @Singleton
-public class DeleteAssignee implements
-    RestModifyView<ChangeResource, Input> {
+public class DeleteAssignee implements RestModifyView<ChangeResource, Input> {
   public static class Input {
 
   }
-  private BatchUpdate.Factory batchUpdateFactory;
+  private final BatchUpdate.Factory batchUpdateFactory;
   private final NotesMigration notesMigration;
   private final ChangeMessagesUtil cmUtil;
   private final Provider<ReviewDb> db;