Rmv unneeded installs and testing flags (will use the flage from the config files)

These weren't used by CI nor were they regularly tested.
If somebody misses something, we can bring them back of course.

This cleanup was triggered with the switch to pytest, and I wanted
to remove everything that was present just for nosetest.

update to actions/setup-python@v1

Add 3.10.0-beta.3 to test matrix.
(beta 4 out, but wouldn't install. Need to force cache emptying?)

Not sure it is picking up the tox.ini

Move pytest before Documentation in workflow

Remove nose

Remove nose tests

Add pytest step to workflow
Add pip install setuptools and wheel
Invoke mypy directly, no need for tox