Remove unused usingOuterActivity parameter from AddTags method

The parameter was only used for DisplayName setting which was removed as redundant.

Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>

Author: Copilot

src/ModelContextProtocol.Core/McpSessionHandler.cs

@@ -467,7 +467,7 @@ public async Task<JsonRpcResponse> SendRequestAsync(JsonRpcRequest request, Canc
         {
             if (addTags)
             {
-                AddTags(ref tags, activity, request, method, target, usingOuterActivity);
+                AddTags(ref tags, activity, request, method, target);
             }
 
             if (_logger.IsEnabled(LogLevel.Trace))
@@ -657,9 +657,6 @@ private static string GetMethodName(JsonRpcMessage message) =>
         };
 
     private void AddTags(ref TagList tags, Activity? activity, JsonRpcMessage message, string method, string? target)
-        => AddTags(ref tags, activity, message, method, target, usingOuterActivity: false);
-
-    private void AddTags(ref TagList tags, Activity? activity, JsonRpcMessage message, string method, string? target, bool usingOuterActivity)
     {
         tags.Add("mcp.method.name", method);
         tags.Add("network.transport", _transportKind);