remove unnecessary function

Author: Haiping Chen

src/Infrastructure/BotSharp.Core/Routing/Reasoning/SequentialReasoner.cs

@@ -234,9 +234,4 @@ private string GetDecomposeTaskPrompt(Agent router)
         {
         });
     }
-
-    public Task<FunctionCallFromLlm> GetNextInstruction(Agent router, string messageId)
-    {
-        throw new NotImplementedException();
-    }
 }