core: Reset archive_manager on shutdown.

This holds the archives which include the SelfNCCH archive which holds the RomFS files. If we don't reset it the LayeredFS class can't get destructed and mods files won't be released.

src/core/core.cpp

@@ -360,6 +360,7 @@ void System::Shutdown() {
     perf_stats.reset();
     rpc_server.reset();
     cheat_engine.reset();
+    archive_manager.reset();
     service_manager.reset();
     dsp_core.reset();
     cpu_core.reset();