[Net\Browser] Check the order of options in the `Browser::post()` method

[AnrDaemon]

Reason: CURLOPT_POSTFIELDS implies setting CURLOPT_POST to true. Setting CURLOPT_POST to true implies setting request method to POST.
Needs checking if setting CURLOPT_POSTFIELDS after CURLOPT_CUSTOMREQUEST with CURLOPT_POST already set resets the request method.