Replace 'referralUrl' with 'url' in WHOIS responses

The 'referralUrl' Datastore field is filled with mostly junk data, whereas
'url' contains real registrar web addresses. This makes the long needed fix to
display the proper url in WHOIS.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=194398003

javatests/google/registry/whois/DomainWhoisResponseTest.java

@@ -70,7 +70,11 @@ public class DomainWhoisResponseTest {
     // Update the registrar to have an IANA ID.
     Registrar registrar =
         persistResource(
-            loadRegistrar("NewRegistrar").asBuilder().setIanaIdentifier(5555555L).build());
+            loadRegistrar("NewRegistrar")
+                .asBuilder()
+                .setUrl("http://my.fake.url")
+                .setIanaIdentifier(5555555L)
+                .build());
 
     persistResource(
         new RegistrarContact.Builder()