Remove redundant xstrdup that results in memory leak

src/slurmctld/proc_req.c

@@ -3656,7 +3656,6 @@ int _launch_batch_step(job_desc_msg_t *job_desc_msg, uid_t uid,
 	launch_msg_ptr->step_id = step_rec->step_id;
 	launch_msg_ptr->gid = job_ptr->group_id;
 	launch_msg_ptr->uid = uid;
-	launch_msg_ptr->nodes = xstrdup(job_ptr->nodes);
 	launch_msg_ptr->nodes = xstrdup(job_ptr->alias_list);
 	launch_msg_ptr->restart_cnt = job_ptr->restart_cnt;
 	if (job_ptr->details) {