fix serving static content issue

Author: dacheng-gao

src/Server/HttpServer.php

@@ -323,7 +323,6 @@ private function tryServeStaticFile(Request $request, Response $response): bool
         // Set response headers
         $response->status(200);
         $response->header('Content-Type', $this->staticFileExtensions[$extension]);
-        $response->header('Content-Length', (string) strlen($content));
 
         // Add cache headers for static files
         $lastModified = filemtime($realPath);