UCGDifficultyUserWidget refactoring

[S1yGus]

SoundMix shouldn't be the property of a widget class.

Cube_Game/Source/Cube_Game/Public/UI/Menu/CGDifficultyUserWidget.h

Lines 28 to 29 in 0d1109a

	UPROPERTY(EditDefaultsOnly, BlueprintReadWrite, Category = "Sound")
	USoundMix* FadeOutSoundMix;