fix initializeresponse payload

Author: TylerLeonhardt

src/Dap.Protocol/Requests/InitializeResponse.cs

@@ -3,12 +3,5 @@
 
 namespace OmniSharp.Extensions.DebugAdapter.Protocol.Requests
 {
-    public class InitializeResponse
-    {
-        /// <summary>
-        /// The capabilities of this debug adapter.
-        /// </summary>
-        [Optional] public Capabilities Body { get; set; }
-    }
-
+    public class InitializeResponse : Capabilities {}
 }