commander: raise stack size

A stack usage of 3000 bytes was observed, therefore it's safer to raise
the commander's stack size by 400 bytes.

src/modules/commander/commander.cpp

@@ -323,7 +323,7 @@ int commander_main(int argc, char *argv[])
 		daemon_task = px4_task_spawn_cmd("commander",
 					     SCHED_DEFAULT,
 					     SCHED_PRIORITY_DEFAULT + 40,
-					     3200,
+					     3600,
 					     commander_thread_main,
 					     (char * const *)&argv[0]);