fix: remove manual Content-Length header for static files

Swoole automatically handles Content-Length when compression is involved.
Manual setting causes warnings when Accept-Encoding header is present.

Author: dacheng-gao

src/Server/HttpServer.php

@@ -360,7 +360,6 @@ 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));
         $response->header('X-Content-Type-Options', 'nosniff');
 
         // Add cache headers for static files