Remove subsystem implementation

This file is unnecessary.

CMakeLists.txt

@@ -84,7 +84,7 @@ add_executable(
     src/packages/game/util/IZ_midi.h
     src/packages/game/net/core/IZ_websocket.h
     src/packages/game/net/core/IZ_websocket.c
-        src/packages/game/net/IZ_net.c src/packages/game/net/IZ_net.h src/packages/game/net/IZ_app.c src/packages/game/net/IZ_app.h src/packages/game/output/video/IZ_app.c src/packages/game/output/video/IZ_app.h src/packages/game/IZ_subsystem.c src/packages/game/IZ_subsystem.h src/packages/game/input/IZ_app.c src/packages/game/input/IZ_app.h)
+        src/packages/game/net/IZ_net.c src/packages/game/net/IZ_net.h src/packages/game/net/IZ_app.c src/packages/game/net/IZ_app.h src/packages/game/output/video/IZ_app.c src/packages/game/output/video/IZ_app.h src/packages/game/IZ_subsystem.h src/packages/game/input/IZ_app.c src/packages/game/input/IZ_app.h)
 
 target_link_libraries(
   game

src/packages/game/IZ_subsystem.c

@@ -1 +0,0 @@
-#include "IZ_subsystem.h"