Config: Add SYSCONF to IsSettingSaveable

SYSCONF very much is saveable. Whether it's in IsSettingSaveable
or not hasn't mattered until now since the SYSCONF settings use
separate config loader code that doesn't check IsSettingSaveable,
but the next commit will require SYSCONF to be marked as saveable.

Source/Core/Core/ConfigLoaders/IsSettingSaveable.cpp

@@ -16,8 +16,8 @@ namespace ConfigLoaders
 {
 bool IsSettingSaveable(const Config::Location& config_location)
 {
-  for (Config::System system :
-       {Config::System::GFX, Config::System::DualShockUDPClient, Config::System::Logger})
+  for (Config::System system : {Config::System::SYSCONF, Config::System::GFX,
+                                Config::System::DualShockUDPClient, Config::System::Logger})
   {
     if (config_location.system == system)
       return true;