Fix a warning

HotkeyManagerEmu.enabled is unused, as everything now uses
HotkeyManagerEmu.s_enabled.

Source/Core/Core/HotkeyManager.h

@@ -39,6 +39,4 @@ namespace HotkeyManagerEmu
 	bool IsEnabled();
 	void Enable(bool enable_toggle);
 	bool IsPressed(int Id, bool held);
-
-	static bool enabled;
 }