requestを呼ぶときに
'proxy' => ''
をoptionsに指定すればOK。
$client = new \GuzzleHttp\Client();
$method = 'POST';
$url= 'http://url.com';
$options = [
'form_params' => [
'param1' => 'AAAAA',
'param2' => 'BBBB',
'param3' => 'CCCC',
],
'proxy' => ''
];
$response = $client->request($method, $url, $options);