service/mm: add missing vector include and update copyright

- Add missing <vector> include for std::vector usage
- Add Citron copyright notice
- Maintain existing include ordering

This is a minor cleanup change to ensure proper header inclusion
and copyright attribution.

src/core/hle/service/mm/mm_u.cpp

@@ -3,6 +3,7 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include <algorithm>
+#include <vector>
 #include "common/logging/log.h"
 #include "core/hle/service/ipc_helpers.h"
 #include "core/hle/service/mm/mm_u.h"