Bug: Multiple Set-Cookie headers in response are not properly handled

Description When using yaak to call an API, there is a bug in cookie handling. According to the HTTP protocol specification, the response header Set-Cookie allows multiple instances. However, when the response returns multiple cookies, yaak only displays one and the rest are lost.

Steps to Reproduce

1. Make an API call using yaak that returns multiple Set-Cookie headers in the response

2. Check the response headers in yaak

3. Observe that only one Set-Cookie header is displayed

Expected Behavior All Set-Cookie headers from the response should be properly displayed and handled.

Actual Behavior Only one Set-Cookie header is shown, while other Set-Cookie headers are missing/lost.

Additional Context This issue affects proper cookie management and session handling when working with APIs that return multiple cookies in their responses.