Remove dead code: options ??= new() after Throw.IfNull(options) in McpServerImpl

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

Author: Copilot

src/ModelContextProtocol.Core/Server/McpServerImpl.cs

@@ -58,8 +58,6 @@ public McpServerImpl(ITransport transport, McpServerOptions options, ILoggerFact
         Throw.IfNull(transport);
         Throw.IfNull(options);
 
-        options ??= new();
-
         _sessionTransport = transport;
         ServerOptions = options;
         Services = serviceProvider;