Tidy up ExpandrecurringBillingEventsAction

Per nickfelt's suggestion on []
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=127193451

javatests/google/registry/testing/ShardableTestCase.java

@@ -23,6 +23,7 @@ import org.junit.Test;
  * sure that we never produces empty shards.
  */
 public abstract class ShardableTestCase {
+
   @Test
   public void testNothing1() {}