Redirect Registrar.referralUrl UI actions to url field

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=196597051

java/google/registry/config/RegistryConfig.java

@@ -1381,13 +1381,6 @@ public final class RegistryConfig {
     return CONFIG_SETTINGS.get().registryPolicy.defaultRegistrarWhoisServer;
   }
 
-  /**
-   * Returns the default referral URL that is used unless registrars have specified otherwise.
-   */
-  public static String getDefaultRegistrarReferralUrl() {
-    return CONFIG_SETTINGS.get().registryPolicy.defaultRegistrarReferralUrl;
-  }
-
   /**
    * Returns the number of {@code EppResourceIndex} buckets to be used.
    */