Remove useless code (#3695)

* [Simple packaging method]packaging method

* [Remove useless code]Maybe dever forgot to delete it

* [Remove useless notes]Wrong commit

Author: Conlin569

common/src/main/java/org/apache/rocketmq/common/sysflag/TopicSysFlag.java

@@ -59,7 +59,4 @@ public static int clearUnitSubFlag(final int sysFlag) {
     public static boolean hasUnitSubFlag(final int sysFlag) {
         return (sysFlag & FLAG_UNIT_SUB) == FLAG_UNIT_SUB;
     }
-
-    public static void main(String[] args) {
-    }
 }