HDFS-14347. [SBN Read] Restore a comment line mistakenly removed in ProtobufRpcEngine. Contributed by Fengnan Li.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/ProtobufRpcEngine.java

@@ -415,6 +415,7 @@ public static ProtobufRpcEngineCallback registerForDeferredResponse() {
      * @param numHandlers the number of method handler threads to run
      * @param verbose whether each call should be logged
      * @param portRangeConfig A config parameter that can be used to restrict
+     * the range of ports used when port is 0 (an ephemeral port)
      * @param alignmentContext provides server state info on client responses
      */
     public Server(Class<?> protocolClass, Object protocolImpl,