fix: switch to gunicorn WSGI server

[satterly]

Description
uwsgi is now in maintenace mode so we need to transition away from it.

Note The project is in maintenance mode (only bugfixes and updates for new languages apis). Do not expect quick answers on github issues and/or pull requests (sorry for that) A big thanks to all of the users and contributors since 2009.

Fixes #448

Changes

• remove all references to uWSGI
• use gunicorn as WSGI server

Checklist

• Pull request is limited to a single purpose
• Code style/formatting is consistent
• All existing tests are passing
• Added new tests related to change
• No unnecessary whitespace changes

Collaboration
When a user creates a pull request from a fork that they own, the user
generally has the authority to decide if other users can commit to the
pull request's compare branch. If the pull request author wants greater
collaboration, they can grant maintainers of the upstream repository
(that is, anyone with push access to the upstream repository) permission
to commit to the pull request's compare branch

See https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/allowing-changes-to-a-pull-request-branch-created-from-a-fork