Revert unnecessary changes

Author: BewareMyPower

microbench/src/main/java/org/apache/pulsar/broker/qos/TopicNameBenchmark.java

@@ -110,16 +110,8 @@ public static String getPattern(String topic) {
         return "^" + Pattern.quote(get(topic).getPartitionedTopicName().toString()) + "$";
     }
 
-    /**
-     * The constructor from a topic name string. The difference from {@link TopicName#get(String)} is that the `get`
-     * method can leverage the built-in cache mechanism, which can be slightly faster, but at the cost of higher JVM
-     * memory usage that could lead to unnecessary GC, as well as potentially OOM in extreme cases.
-     * You can benchmark `TopicName.get(topic)` and `new TopicName(topic)` to see the actual performance gap.
-     *
-     * @param completeTopicName the topic name
-     */
     @SuppressFBWarnings("DCN_NULLPOINTER_EXCEPTION")
-    public TopicName(String completeTopicName) {
+    private TopicName(String completeTopicName) {
         try {
             // The topic name can be in two different forms, one is fully qualified topic name,
             // the other one is short topic name