Remove dnsRefreshRequestTime from EppResources (#1943)

We have decided to use a separate table (#1940) to track DNS refresh requests
due to performance reasons.

See: go/registry-pull-queue-redesign

core/src/test/java/google/registry/model/domain/DomainTest.java

@@ -221,7 +221,6 @@ public class DomainTest {
                             "TheRegistrar",
                             oneTimeBillKey))
                     .setAutorenewEndTime(Optional.of(fakeClock.nowUtc().plusYears(2)))
-                    .setDnsRefreshRequestTime(Optional.of(fakeClock.nowUtc()))
                     .build()));
   }
 

core/src/test/java/google/registry/model/history/DomainHistoryTest.java

@@ -41,8 +41,6 @@ import google.registry.model.reporting.DomainTransactionRecord;
 import google.registry.model.reporting.DomainTransactionRecord.TransactionReportField;
 import google.registry.model.reporting.HistoryEntry;
 import google.registry.util.SerializeUtils;
-import java.util.Optional;
-import org.joda.time.DateTime;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
@@ -97,7 +95,6 @@ public class DomainHistoryTest extends EntityTestCase {
             .asBuilder()
             .setNameservers(host.createVKey())
             .setDsData(ImmutableSet.of(DomainDsData.create(1, 2, 3, new byte[] {0, 1, 2})))
-            .setDnsRefreshRequestTime(Optional.of(DateTime.parse("2020-03-09T16:40:00Z")))
             .build();
     insertInDb(domain);
     return domain;