Fix access to private property cookies in HttpResponse class

[gomzyakov]

Description

When we call method:

$response = $this->kit->getAccessToken();

We get error:

Cannot access private property Afiqiqmal\HuaweiPush\Client\HttpResponse::$cookies

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I wrote unit tests for my code (if tests is required for my changes)
• I have made changes in CHANGELOG.md file