setup.py - remove insecure requests to https://pypi.org/pypi/python-appimage/json

[manfred-kaiser]

the request to https://pypi.org/pypi/python-appimage/json should be removed, because it breaks workflows, when running without an internet connection.

Another reason is, that you are using _create_unverified_context, which disables certificate validation.

This makes using you package insecure and prone to man in the middle attacks.

Determine the version number this way also breaks reproducible builds.

[hendursaga]

Is the security aspect of this resolved yet?