Increase Cloud DNS rate limit to 50 QPS

Following b/74072938, our quota for our main projects (prod, sandbox, alpha) is now 5000 queries per 100s, which allows us to increase our client-side rate limit accordingly.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=188026911

java/google/registry/dns/writer/clouddns/CloudDnsWriterModule.java

@@ -89,7 +89,7 @@ public final class CloudDnsWriterModule {
   static RateLimiter provideRateLimiter() {
     // This is the default max QPS for Cloud DNS. It can be increased by contacting the team
     // via the Quotas page on the Cloud Console.
-    int cloudDnsMaxQps = 20;
+    int cloudDnsMaxQps = 50;
     return RateLimiter.create(cloudDnsMaxQps);
   }