Disabling internal audio to use external audio system shows "Audio Device Manager Initialization Failed!" warning

In addition, we can find 
"Main audio device could not be initialized. Please check the value for AudioDeviceModuleName and AudioMixerModuleName in [Platform]Engine.ini."
log message in the engine.
It is appropriate to remove the AudioDeviceModuleName since it is no longer referenced anywhere in the engine.

1. Open Confing/Windows/WindowsEngine.ini
2. Put following configs

   ; WindowsEngine.ini
   [Audio]
   AudioDeviceModuleName=
   AudioMixerModuleName=
   

3. launch the editor
4. see logs

Result:

Even though the internal audio system is intentionally disabled, "Audio Device Manager Initialization Failed!" warning is output.