gitadora: (arena model) flip realtek option (#733)

## Link to GitHub Issue or related Pull Request, if one exists
#730 

## Description of change
Flip the option - enable the Realtek hack by default, unless the user
chooses not to.

## Testing
Tested ASIO path and WASAPI path. WASAPI path should be unaffected as
the game just picks the default audio device.

src/spice2x/hooks/audio/audio.cpp

@@ -47,7 +47,7 @@ namespace hooks::audio {
     bool USE_DUMMY = false;
     WAVEFORMATEXTENSIBLE FORMAT {};
     std::optional<Backend> BACKEND = std::nullopt;
-    bool FAKE_REALTEK_RENDER_DEVICE = false;
+    bool INJECT_FAKE_REALTEK_AUDIO = false;
     std::optional<size_t> ASIO_DRIVER_ID = std::nullopt;
     std::string ASIO_DRIVER_NAME = "";
     bool ASIO_FORCE_UNLOAD_ON_STOP = false;