[improve] [broker] Optimize performance for checking max topics when …

…the topic is a system topic (apache#23185)

(cherry picked from commit 73433cd)

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/BrokerService.java

@@ -3728,6 +3728,9 @@ public CompletableFuture<SchemaVersion> deleteSchema(TopicName topicName) {
     }
 
     private CompletableFuture<Void> checkMaxTopicsPerNamespace(TopicName topicName, int numPartitions) {
+        if (isSystemTopic(topicName)) {
+            return CompletableFuture.completedFuture(null);
+        }
         return pulsar.getPulsarResources().getNamespaceResources()
                 .getPoliciesAsync(topicName.getNamespaceObject())
                 .thenCompose(optPolicies -> {