Upgrade actions/checkout and actions/setup-python

[cclauss]

https://github.com/actions/checkout/releases
https://github.com/actions/setup-python/releases

[mattip]

Not really connected to this PR, but...

Appveyor builds are failing with

git clone git://github.com/ogrisel/python-appveyor-demo.git
Cloning into 'python-appveyor-demo'...
fatal: remote error: 
  The unauthenticated git protocol on port 9418 is no longer supported.
Please see https://github.blog/2021-09-01-improving-git-protocol-security-github/ for more information.

which is coming from

multibuild/.appveyor.yml

Line 54 in fab0a08

- git clone git://github.com/ogrisel/python-appveyor-demo.git

Shouldn't that be https instead? git clone git:// -> git clone https://

[mattip]

Thanks @cclauss