When resolving a transfer to SERVER_CANCELLED (on delete) still pass in a time

Currently we pass in null. However, from the spec:

<domain:acDate> element that contains the date and time of a
      required or completed response.  For a PENDING request, the value
      identifies the date and time by which a response is required
      before an automated response action will be taken by the server.
      For all other status types, the value identifies the date and time
      when the request was completed."
          - https://tools.ietf.org/html/rfc5731#page-16, section 3.1.3

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=139363370

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

@@ -537,6 +537,8 @@ public class DomainDeleteFlowTest extends ResourceFlowTestCase<DomainDeleteFlow,
     assertThat(domain.getTransferData().getServerApproveBillingEvent()).isNull();
     assertThat(domain.getTransferData().getServerApproveAutorenewEvent()).isNull();
     assertThat(domain.getTransferData().getServerApproveAutorenewPollMessage()).isNull();
+    assertThat(domain.getTransferData().getPendingTransferExpirationTime())
+        .isEqualTo(clock.nowUtc());
     assertThat(ofy().load().key(oldTransferData.getServerApproveBillingEvent()).now()).isNull();
     assertThat(ofy().load().key(oldTransferData.getServerApproveAutorenewEvent()).now()).isNull();
     assertThat(ofy().load().key(oldTransferData.getServerApproveAutorenewPollMessage()).now())