removed unused reference

Author: StephenHodgson

Assets/MixedRealityToolkit-SDK/Features/Input/MixedRealityInputManager.cs

@@ -7,7 +7,6 @@
 using Microsoft.MixedReality.Toolkit.Internal.Definitions.Utilities;
 using Microsoft.MixedReality.Toolkit.Internal.EventDatum.Input;
 using Microsoft.MixedReality.Toolkit.Internal.Extensions;
-using Microsoft.MixedReality.Toolkit.Internal.Interfaces;
 using Microsoft.MixedReality.Toolkit.Internal.Interfaces.Devices;
 using Microsoft.MixedReality.Toolkit.Internal.Interfaces.InputSystem;
 using Microsoft.MixedReality.Toolkit.Internal.Interfaces.InputSystem.Handlers;