remove unused files.

src/DotNetCore.CAP/IFetchedMessage.cs

-// Copyright (c) .NET Core Community. All rights reserved.
-// Licensed under the MIT License. See License.txt in the project root for license information.
-
-using System;
-using DotNetCore.CAP.Models;
-
-namespace DotNetCore.CAP
-{
-    public interface IFetchedMessage : IDisposable
-    {
-        int MessageId { get; }
-
-        MessageType MessageType { get; }
-
-        void RemoveFromQueue();
-
-        void Requeue();
-    }
-}
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