Use config settings for DNS TTL values across all code

Attending to this old bug will improve our ability to perform zone comparisons between Datastore and the DNS provider. Right now, zone comparison finds some bogus differences, because the TTL we send to the DNS subsystem doesn't match the TTL we use when generating our local dump files.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=164635557

java/google/registry/dns/writer/dnsupdate/DnsUpdateConfigModule.java

@@ -41,13 +41,4 @@ public class DnsUpdateConfigModule {
   public static Duration provideDnsUpdateTimeout() {
     return Duration.standardSeconds(30);
   }
-
-  /**
-   * The DNS time-to-live (TTL) for resource records created by the registry.
-   */
-  @Provides
-  @Config("dnsUpdateTimeToLive")
-  public static Duration provideDnsUpdateTimeToLive() {
-    return Duration.standardHours(2);
-  }
 }