Remove temporary handling of invalid billing events

The bad prober domain data has since been deleted, so we no longer need
to handle the case where these Keys point to entities that don't exist.

This mostly reverses []

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=168687701

javatests/google/registry/flows/domain/DomainDeleteFlowTest.java

@@ -511,20 +511,6 @@ public class DomainDeleteFlowTest extends ResourceFlowTestCase<DomainDeleteFlow,
     assertThat(domain.getTransferData()).isEqualTo(TransferData.EMPTY);
   }
 
-  //TODO(b/27472322): Delete test handling recurring being null once bad data is cleaned from prod.
-  @Test
-  public void testSuccess_nullAutorenewBillingEvent_isIgnore() throws Exception {
-    setClientIdForFlow("TheRegistrar");
-    setUpSuccessfulTest();
-    ofy().deleteWithoutBackup().key(domain.getAutorenewBillingEvent()).now();
-    ofy().clearSessionCache();
-    clock.advanceOneMilli();
-    runFlowAssertResponse(readFile("domain_delete_response_pending.xml"));
-    // If the previous statement doesn't throw an error, then the test is successful.
-    assertThat(ofy().load().key(reloadResourceByForeignKey().getAutorenewBillingEvent()).now())
-        .isNull();
-  }
-
   @Test
   public void testSuccess_pendingTransfer() throws Exception {
     setClientIdForFlow("TheRegistrar");