Remove special Cloud DNS configuration from sandbox.

Removing this stanza from the config will cause sandbox to write to production
cloud dns, which is what we want.

Likewise, exclude sandbox in addition to production in the create_cdns_tld
command from the environments that point to staging.

Cloud DNS has 3 environments that we would consider using:
- staging which is reset every week, so we can't use it for sandbox
- testing, which is not accessible from external App Engine
- production

Because of the difficulties with the first two, we've decided to use production.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=208834786

java/google/registry/tools/CreateCdnsTld.java

@@ -116,7 +116,8 @@ class CreateCdnsTld extends ConfirmingCommand {
 
     Dns.Builder builder =
         new Dns.Builder(httpTransport, jsonFactory, credential).setApplicationName(projectId);
-    if (RegistryToolEnvironment.get() != RegistryToolEnvironment.PRODUCTION) {
+    if (RegistryToolEnvironment.get() != RegistryToolEnvironment.PRODUCTION
+        && RegistryToolEnvironment.get() != RegistryToolEnvironment.SANDBOX) {
       builder
           .setRootUrl("https://staging-www.sandbox.googleapis.com")
           .setServicePath("dns/v2beta1_staging/projects/");