[hle/ns] fix build error due to missing async_result.h (#4440)

We may have merged quite a bit too fast before letting CI finish.

Signed-off-by: lizzie <lizzie@eden-emu.dev>

- [x] I have read and followed the [Contribution Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/CONTRIBUTING.md#code-contributions).
- [x] I have read and followed the [AI Policy](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/docs/policies/AI.md)
- [x] I have read and followed the [Coding Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/docs/policies/Coding.md) to the best of my ability.

-------------------

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4440
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>

src/core/hle/service/ns/async_result.cpp

@@ -2,7 +2,7 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 #include "core/hle/service/cmif_serialization.h"
-#include "core/hle/service/ns/i_async_result.h"
+#include "core/hle/service/ns/async_result.h"
 
 #include <cstring>