drop dependency on unmaintained httpretty

[stanislavlevin]

httpretty is tests dependency of this project.

Unfortunately, it's no longer maintained:
gabrielfalcao/HTTPretty#482

As it's suggested in the aforementioned issue it can be probably replaced with mocket:
https://github.com/mindflayer/python-mocket?tab=readme-ov-file#httpretty-compatibility-layer

Examples of replacement with responses:
canonical/cloud-init#1720
PyGithub/PyGithub#3087

[jdepoix]

Hi @stanislavlevin,

since it just is a test dependency and is running fine in the current version I don't think it's high priority to migrate it, but I am open to accepting PRs on this!