YARN-11435. Fix CheckStyle.

Author: slfan1989

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-router/src/main/java/org/apache/hadoop/yarn/server/router/security/RouterDelegationTokenSecretManager.java

@@ -67,6 +67,7 @@ public class RouterDelegationTokenSecretManager
    * @param delegationTokenRenewInterval       how often the tokens must be renewed
    *                                           in milliseconds
    * @param delegationTokenRemoverScanInterval how often the tokens are scanned
+   * @param conf Configuration.
    */
   public RouterDelegationTokenSecretManager(long delegationKeyUpdateInterval,
       long delegationTokenMaxLifetime, long delegationTokenRenewInterval,