Remove useless status in DomainDeleteFlow

Domains can't have LINKED status.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=140389416

java/google/registry/flows/domain/DomainDeleteFlow.java

@@ -91,7 +91,6 @@ import org.joda.time.DateTime;
 public final class DomainDeleteFlow implements TransactionalFlow {
 
   private static final ImmutableSet<StatusValue> DISALLOWED_STATUSES = ImmutableSet.of(
-      StatusValue.LINKED,
       StatusValue.CLIENT_DELETE_PROHIBITED,
       StatusValue.PENDING_DELETE,
       StatusValue.SERVER_DELETE_PROHIBITED);