type:ignore comments are used to silence mypy errors
let's remove the ones that are not anymore necessary

related: cubicweb#528

These types are not supposed to be accessed by client code.

TypeVars should be referenced at least twice otherwise they have no effect.

Add a job that will:
- clone the last Cubicweb version
- update rql requirement within Cubicweb's setup.py
- finally, run tox -e py3-server

See #8

Searched across all projects on the forge.

This allows to support pyright which doesn't support sub-typing of conditional types.
See https://github.com/microsoft/pyright/issues/2047.

Not a breaking change since no version has been released.