Dataman: Remove excessive stack allocation

src/modules/dataman/dataman.c

@@ -861,7 +861,7 @@ start(void)
 	px4_sem_init(&g_init_sema, 1, 0);
 
 	/* start the worker thread with low priority for disk IO */
-	if ((task = px4_task_spawn_cmd("dataman", SCHED_DEFAULT, SCHED_PRIORITY_DEFAULT - 10, 1500, task_main, NULL)) <= 0) {
+	if ((task = px4_task_spawn_cmd("dataman", SCHED_DEFAULT, SCHED_PRIORITY_DEFAULT - 10, 1200, task_main, NULL)) <= 0) {
 		warn("task start failed");
 		return -1;
 	}