mvc: configdStream: actually, ob_end_flush() is still necessary

Turns out there is still implicit buffering happening, the exception
thrown is due to a lack of error handling on the Phalcon side. Even
the PHP docs suggest silencing this with '@'.

This reverts commit 7c05e52.

src/opnsense/mvc/app/controllers/OPNsense/Base/ApiControllerBase.php

@@ -180,7 +180,7 @@ protected function configdStream(
         foreach ($headers as $header) {
             header($header);
         }
-
+        ob_end_flush();
         fpassthru($response);
     }