Remove unused file.

src/InteractiveWindow/VisualStudio/Utils.cs

-// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
-
-using System;
-using System.Diagnostics;
-
-namespace Microsoft.VisualStudio.InteractiveWindow.Shell
-{
-    internal static class SpecializedCollections
-    {
-        internal static class Empty
-        {
-            internal class Array<T>
-            {
-                public static readonly T[] Instance = Array.Empty<T>();
-            }
-        }
-
-        public static T[] EmptyArray<T>()
-        {
-            return Empty.Array<T>.Instance;
-        }
-    }
-
-    internal static class ExceptionUtilities
-    {
-        [DebuggerDisplay("Unreachable")]
-        public static Exception Unreachable
-        {
-            get
-            {
-                Debug.Fail("This code path should not be reachable");
-                return new InvalidOperationException();
-            }
-        }
-    }
-}

src/InteractiveWindow/VisualStudio/VisualStudioInteractiveWindow.csproj

@@ -133,7 +133,6 @@
     <Compile Include="IVsInteractiveWindowOleCommandTargetProvider.cs" />
     <Compile Include="MenuIds.cs" />
     <Compile Include="ProvideInteractiveWindowAttribute.cs" />
-    <Compile Include="Utils.cs" />
     <Compile Include="VsInteractiveWindow.cs" />
     <Compile Include="VsInteractiveWindowCommandFilter.cs" />
     <Compile Include="VsInteractiveWindowExtensions.cs" />