refactor: remove curl_close as has no effect since PHP 8.0 (codeigniter4#9683)

Author: ddevsr

system/HTTP/CURLRequest.php

@@ -733,8 +733,6 @@ protected function sendRequest(array $curlOptions = []): string
             throw HTTPException::forCurlError((string) curl_errno($ch), curl_error($ch));
         }
 
-        curl_close($ch);
-
         return $output;
     }